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Li X, Li Z, Li M, Li J, Wang Q, Wang S, Li S, Li H. Transcriptomic and metabolomic analysis reveals the influence of carbohydrates on lignin degradation mediated by Bacillus amyloliquefaciens. Front Microbiol 2024; 15:1224855. [PMID: 38333584 PMCID: PMC10850570 DOI: 10.3389/fmicb.2024.1224855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 01/05/2024] [Indexed: 02/10/2024] Open
Abstract
Introduction Ligninolytic bacteria can secrete extracellular enzymes to depolymerize lignin into small-molecular aromatics that are subsequently metabolized and funneled into the TCA cycle. Carbohydrates, which are the preferred carbon sources of bacteria, influence the metabolism of lignin-derived aromatics through bacteria. Methods In this study, untargeted metabolomics and transcriptomics analyses were performed to investigate the effect of carbohydrates on lignin degradation mediated by Bacillus amyloliquefaciens MN-13, a strain with lignin-degrading activity that was isolated in our previous work. Results The results demonstrated that the cell growth of the MN-13 strain and lignin removal were promoted when carbohydrates such as glucose and sodium carboxymethyl cellulose were added to an alkaline lignin-minimal salt medium (AL-MSM) culture. Metabolomics analysis showed that lignin depolymerization took place outside the cells, and the addition of glucose regulated the uptake and metabolism of lignin-derived monomers and activated the downstream metabolism process in cells. In the transcriptomics analysis, 299 DEGs were screened after 24 h of inoculation in AL-MSM with free glucose and 2 g/L glucose, respectively, accounting for 8.3% of the total amount of annotated genes. These DEGs were primarily assigned to 30 subcategories, including flagellar assembly, the PTS system, RNA degradation, glycolysis/gluconeogenesis, the TCA cycle, pyruvate metabolism, and tryptophan metabolism. These subcategories were closely associated with the cell structure, generation of cellular energy, and precursors for biosynthetic pathways, based on a - log 10 (P adjust) value in the KEGG pathway analysis. Conclusion In summary, the addition of glucose increased lignin degradation mediated by the MN-13 strain through regulating glycolysis, TCA cycle, and central carbon metabolism.
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Affiliation(s)
- Xiaodan Li
- College of Life Sciences, Hebei Agricultural University, Baoding, China
| | - Zhuofan Li
- College of Life Sciences, Hebei Agricultural University, Baoding, China
| | - Ming Li
- College of Life Sciences, Hebei Agricultural University, Baoding, China
| | - Jingwen Li
- College of Life Sciences, Hebei Agricultural University, Baoding, China
| | - Quan Wang
- College of Life Sciences, Hebei Agricultural University, Baoding, China
- Hebei Forage Microbial Technology Innovation Center, Baoding, Hebei, China
| | - Shuxiang Wang
- College of Life Sciences, Hebei Agricultural University, Baoding, China
- Hebei Forage Microbial Technology Innovation Center, Baoding, Hebei, China
| | - Shuna Li
- College of Life Sciences, Hebei Agricultural University, Baoding, China
- Hebei Forage Microbial Technology Innovation Center, Baoding, Hebei, China
| | - Hongya Li
- College of Life Sciences, Hebei Agricultural University, Baoding, China
- Hebei Forage Microbial Technology Innovation Center, Baoding, Hebei, China
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2
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Zhao ZM, Liu ZH, Zhang T, Meng R, Gong Z, Li Y, Hu J, Ragauskas AJ, Li BZ, Yuan YJ. Unleashing the capacity of Rhodococcus for converting lignin into lipids. Biotechnol Adv 2024; 70:108274. [PMID: 37913947 DOI: 10.1016/j.biotechadv.2023.108274] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 09/11/2023] [Accepted: 10/22/2023] [Indexed: 11/03/2023]
Abstract
Bioconversion of bioresources/wastes (e.g., lignin, chemical pulping byproducts) represents a promising approach for developing a bioeconomy to help address growing energy and materials demands. Rhodococcus, a promising microbial strain, utilizes numerous carbon sources to produce lipids, which are precursors for synthesizing biodiesel and aviation fuels. However, compared to chemical conversion, bioconversion involves living cells, which is a more complex system that needs further understanding and upgrading. Various wastes amenable to bioconversion are reviewed herein to highlight the potential of Rhodococci for producing lipid-derived bioproducts. In light of the abundant availability of these substrates, Rhodococcus' metabolic pathways converting them to lipids are analyzed from a "beginning-to-end" view. Based on an in-depth understanding of microbial metabolic routes, genetic modifications of Rhodococcus by employing emerging tools (e.g., multiplex genome editing, biosensors, and genome-scale metabolic models) are presented for promoting the bioconversion. Co-solvent enhanced lignocellulose fractionation (CELF) strategy facilitates the generation of a lignin-derived aromatic stream suitable for the Rhodococcus' utilization. Novel alkali sterilization (AS) and elimination of thermal sterilization (ETS) approaches can significantly enhance the bioaccessibility of lignin and its derived aromatics in aqueous fermentation media, which promotes lipid titer significantly. In order to achieve value-added utilization of lignin, biodiesel and aviation fuel synthesis from lignin and lipids are further discussed. The possible directions for unleashing the capacity of Rhodococcus through synergistically modifying microbial strains, substrates, and fermentation processes are proposed toward a sustainable biological lignin valorization.
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Affiliation(s)
- Zhi-Min Zhao
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States; Key Laboratory of Ecology and Resource Use of the Mongolian Plateau (Ministry of Education), School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Zhi-Hua Liu
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Tongtong Zhang
- Key Laboratory of Ecology and Resource Use of the Mongolian Plateau (Ministry of Education), School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Rongqian Meng
- Key Laboratory of Ecology and Resource Use of the Mongolian Plateau (Ministry of Education), School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Zhiqun Gong
- Key Laboratory of Ecology and Resource Use of the Mongolian Plateau (Ministry of Education), School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Yibing Li
- Key Laboratory of Ecology and Resource Use of the Mongolian Plateau (Ministry of Education), School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Jing Hu
- Key Laboratory of Ecology and Resource Use of the Mongolian Plateau (Ministry of Education), School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
| | - Arthur J Ragauskas
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States; Joint Institute of Biological Science, Biosciences Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, United States; Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, United States.
| | - Bing-Zhi Li
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
| | - Ying-Jin Yuan
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
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Li X, Gluth A, Feng S, Qian WJ, Yang B. Harnessing redox proteomics to study metabolic regulation and stress response in lignin-fed Rhodococci. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:180. [PMID: 37986172 PMCID: PMC10662689 DOI: 10.1186/s13068-023-02424-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 11/02/2023] [Indexed: 11/22/2023]
Abstract
BACKGROUND Rhodococci are studied for their bacterial ligninolytic capabilities and proclivity to accumulate lipids. Lignin utilization is a resource intensive process requiring a variety of redox active enzymes and cofactors for degradation as well as defense against the resulting toxic byproducts and oxidative conditions. Studying enzyme expression and regulation between carbon sources will help decode the metabolic rewiring that stymies lignin to lipid conversion in these bacteria. Herein, a redox proteomics approach was applied to investigate a fundamental driver of carbon catabolism and lipid anabolism: redox balance. RESULTS A consortium of Rhodococcus strains was employed in this study given its higher capacity for lignin degradation compared to monocultures. This consortium was grown on glucose vs. lignin under nitrogen limitation to study the importance of redox balance as it relates to nutrient availability. A modified bottom-up proteomics workflow was harnessed to acquire a general relationship between protein abundance and protein redox states. Global proteomics results affirm differential expression of enzymes involved in sugar metabolism vs. those involved in lignin degradation and aromatics metabolism. As reported previously, several enzymes in the lipid biosynthetic pathways were downregulated, whereas many involved in β-oxidation were upregulated. Interestingly, proteins involved in oxidative stress response were also upregulated perhaps in response to lignin degradation and aromatics catabolism, which require oxygen and reactive oxygen species and generate toxic byproducts. Enzymes displaying little-to-no change in abundance but differences in redox state were observed in various pathways for carbon utilization (e.g., β‑ketoadipate pathway), lipid metabolism, as well as nitrogen metabolism (e.g., purine scavenging/synthesis), suggesting potential mechanisms of redox-dependent regulation of metabolism. CONCLUSIONS Efficient lipid production requires a steady carbon and energy flux while balancing fundamental requirements for enzyme production and cell maintenance. For lignin, we theorize that this balance is difficult to establish due to resource expenditure for enzyme production and stress response. This is supported by significant changes to protein abundances and protein cysteine oxidation in various metabolic pathways and redox processes.
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Affiliation(s)
- Xiaolu Li
- Bioproducts, Sciences, and Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Austin Gluth
- Bioproducts, Sciences, and Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA
| | - Song Feng
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Wei-Jun Qian
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Bin Yang
- Bioproducts, Sciences, and Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA.
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
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4
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Tang YJ, Moon TS. Mining microbial metabolism. Nat Chem Biol 2023; 19:544-545. [PMID: 36747057 DOI: 10.1038/s41589-023-01257-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Yinjie J Tang
- Washington University in St. Louis, St. Louis, MO, USA.
| | - Tae Seok Moon
- Washington University in St. Louis, St. Louis, MO, USA.
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Troiano DT, Hofmann T, Brethauer S, Studer MHP. Toward optimal use of biomass as carbon source for chemical bioproduction. Curr Opin Biotechnol 2023; 81:102942. [PMID: 37062153 DOI: 10.1016/j.copbio.2023.102942] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 03/04/2023] [Accepted: 03/17/2023] [Indexed: 04/18/2023]
Abstract
Biomass is widely identified as a promising, renewable replacement for fossil feedstocks in the production of energy, fuels, and chemicals. However, the sustainable supply of biomass is limited. Economic and ecological criteria support prioritization of biomass as a carbon source for organic chemicals; however, utilization for energy currently dominates. Therefore, to optimize the use of available biomass feedstock, biorefining development must focus on high carbon efficiencies and enabling the conversion of all biomass fractions, including lignin and fermentation-derived CO2. Additionally, novel technological platforms should allow the incorporation of nontraditional, currently underutilized carbon feedstocks (e.g. manure) into biorefining processes. To this end, funneling of waste feedstocks to a single product (e.g. methane) and subsequent conversion to chemicals is a promising approach.
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Affiliation(s)
- Derek T Troiano
- School of Agricultural, Forest, and Food Sciences, Bern University of Applied Sciences, CH-3052 Zollikofen, Switzerland
| | - Tobias Hofmann
- School of Agricultural, Forest, and Food Sciences, Bern University of Applied Sciences, CH-3052 Zollikofen, Switzerland
| | - Simone Brethauer
- School of Agricultural, Forest, and Food Sciences, Bern University of Applied Sciences, CH-3052 Zollikofen, Switzerland
| | - Michael H-P Studer
- School of Agricultural, Forest, and Food Sciences, Bern University of Applied Sciences, CH-3052 Zollikofen, Switzerland.
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6
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Sharma V, Tsai ML, Nargotra P, Chen CW, Sun PP, Singhania RR, Patel AK, Dong CD. Journey of lignin from a roadblock to bridge for lignocellulose biorefineries: A comprehensive review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 861:160560. [PMID: 36574559 DOI: 10.1016/j.scitotenv.2022.160560] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 11/06/2022] [Accepted: 11/24/2022] [Indexed: 06/17/2023]
Abstract
The grave concerns arisen as a result of environmental pollution and diminishing fossil fuel reserves in the 21st century have shifted the focus on the use of sustainable and environment friendly alternative resources. Lignocellulosic biomass constituted by cellulose, hemicellulose and lignin is an abundantly available natural bioresource. Lignin, a natural biopolymer has over the years gained much importance as a high value material with commercial importance. The present review provides an in-depth knowledge on the journey of lignin from being considered a roadblock to a bridge connecting diverse industries with widescale applications. The successful valorization of lignin for the production of bio-based platform chemicals and fuels has been the subject of intensive investigation. A deeper understanding of lignin characteristics and factors governing the biomass conversion into valuable products can support improved biomass consumption. The components of lignocellulosic biomass might be totally transformed into a variety of value-added products with the improvements in bioprocess techniques that valorize lignin. In this review, the recent advances in the lignin extraction and depolymerization methods that may help in achieving the cost-economics of the bioprocess are summarized and compared. The industrial potential of lignin-derived products such as aromatics, biopolymers, biofuels and agrochemicals are also outlined. Additionally, assessment of the recent research trends in lignin valorization into value-added chemicals has been done and present scenario of technological-industrial applications of lignin with economic perspectives is highlighted.
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Affiliation(s)
- Vishal Sharma
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan; Department of Seafood Science, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan
| | - Mei-Ling Tsai
- Department of Seafood Science, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan
| | - Parushi Nargotra
- Department of Seafood Science, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan
| | - Chiu-Wen Chen
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan; Institute of Aquatic Science and Technology, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan
| | - Pei-Pei Sun
- Department of Seafood Science, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan
| | - Reeta Rani Singhania
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan; Centre for Energy and Environmental Sustainability, Lucknow 226 029, India
| | - Anil Kumar Patel
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan; Centre for Energy and Environmental Sustainability, Lucknow 226 029, India
| | - Cheng-Di Dong
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan; Institute of Aquatic Science and Technology, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan.
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7
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Ding Z, Kumar Awasthi S, Kumar M, Kumar V, Mikhailovich Dregulo A, Yadav V, Sindhu R, Binod P, Sarsaiya S, Pandey A, Taherzadeh MJ, Rathour R, Singh L, Zhang Z, Lian Z, Kumar Awasthi M. A thermo-chemical and biotechnological approaches for bamboo waste recycling and conversion to value added product: Towards a zero-waste biorefinery and circular bioeconomy. FUEL 2023; 333:126469. [DOI: 10.1016/j.fuel.2022.126469] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/20/2023]
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8
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Xu Z, Peng B, Kitata RB, Nicora CD, Weitz KK, Pu Y, Shi T, Cort JR, Ragauskas AJ, Yang B. Understanding of bacterial lignin extracellular degradation mechanisms by Pseudomonas putida KT2440 via secretomic analysis. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:117. [PMID: 36316752 PMCID: PMC9620641 DOI: 10.1186/s13068-022-02214-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Accepted: 10/12/2022] [Indexed: 11/07/2022]
Abstract
BACKGROUND Bacterial lignin degradation is believed to be primarily achieved by a secreted enzyme system. Effects of such extracellular enzyme systems on lignin structural changes and degradation pathways are still not clearly understood, which remains as a bottleneck in the bacterial lignin bioconversion process. RESULTS This study investigated lignin degradation using an isolated secretome secreted by Pseudomonas putida KT2440 that grew on glucose as the only carbon source. Enzyme assays revealed that the secretome harbored oxidase and peroxidase/Mn2+-peroxidase capacity and reached the highest activity at 120 h of the fermentation time. The degradation rate of alkali lignin was found to be only 8.1% by oxidases, but increased to 14.5% with the activation of peroxidase/Mn2+-peroxidase. Gas chromatography-mass spectrometry (GC-MS) and two-dimensional 1H-13C heteronuclear single-quantum coherence (HSQC) NMR analysis revealed that the oxidases exhibited strong C-C bond (β-β, β-5, and β-1) cleavage. The activation of peroxidases enhanced lignin degradation by stimulating C-O bond (β-O-4) cleavage, resulting in increased yields of aromatic monomers and dimers. Further mass spectrometry-based quantitative proteomics measurements comprehensively identified different groups of enzymes particularly oxidoreductases in P. putida secretome, including reductases, peroxidases, monooxygenases, dioxygenases, oxidases, and dehydrogenases, potentially contributed to the lignin degradation process. CONCLUSIONS Overall, we discovered that bacterial extracellular degradation of alkali lignin to vanillin, vanillic acid, and other lignin-derived aromatics involved a series of oxidative cleavage, catalyzed by active DyP-type peroxidase, multicopper oxidase, and other accessory enzymes. These results will guide further metabolic engineering design to improve the efficiency of lignin bioconversion.
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Affiliation(s)
- Zhangyang Xu
- grid.451303.00000 0001 2218 3491Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, ashington State University Tri-Cities, Joint Appointment: Pacific Northwest National Laboratory, 2710 Crimson Way, Richland, WA 99354 USA
| | - Bo Peng
- grid.451303.00000 0001 2218 3491Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, ashington State University Tri-Cities, Joint Appointment: Pacific Northwest National Laboratory, 2710 Crimson Way, Richland, WA 99354 USA
| | - Reta Birhanu Kitata
- grid.451303.00000 0001 2218 3491Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 USA
| | - Carrie D. Nicora
- grid.451303.00000 0001 2218 3491Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 USA
| | - Karl K. Weitz
- grid.451303.00000 0001 2218 3491Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 USA
| | - Yunqiao Pu
- grid.135519.a0000 0004 0446 2659Joint Institute for Biological Sciences, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Tujin Shi
- grid.451303.00000 0001 2218 3491Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 USA
| | - John R. Cort
- grid.451303.00000 0001 2218 3491Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 USA
| | - Arthur J. Ragauskas
- grid.135519.a0000 0004 0446 2659Joint Institute for Biological Sciences, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA ,grid.411461.70000 0001 2315 1184Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996 USA ,grid.411461.70000 0001 2315 1184Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, University of Tennessee Institute of Agriculture, Knoxville, TN 37996 USA
| | - Bin Yang
- grid.451303.00000 0001 2218 3491Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, ashington State University Tri-Cities, Joint Appointment: Pacific Northwest National Laboratory, 2710 Crimson Way, Richland, WA 99354 USA ,grid.451303.00000 0001 2218 3491Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 USA
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Deciphering the transcriptional regulation of the catabolism of lignin-derived aromatics in Rhodococcus opacus PD630. Commun Biol 2022; 5:1109. [PMID: 36261484 DOI: 10.1038/s42003-022-04069-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 10/04/2022] [Indexed: 11/08/2022] Open
Abstract
Rhodococcus opacus PD630 has considerable potential as a platform for valorizing lignin due to its innate "biological funneling" pathways. However, the transcriptional regulation of the aromatic catabolic pathways and the mechanisms controlling aromatic catabolic operons in response to different aromatic mixtures are still underexplored. Here, we identified and studied the transcription factors for aromatic degradation using GFP-based sensors and comprehensive deletion analyses. Our results demonstrate that the funneling pathways for phenol, guaiacol, 4-hydroxybenzoate, and vanillate are controlled by transcriptional activators. The two different branches of the β-ketoadipate pathway, however, are controlled by transcriptional repressors. Additionally, promoter activity assays revealed that the substrate hierarchy in R. opacus may be ascribed to the transcriptional cross-regulation of the individual aromatic funneling pathways. These results provide clues to clarify the molecule-level mechanisms underlying the complex regulation of aromatic catabolism, which facilitates the development of R. opacus as a promising chassis for valorizing lignin.
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10
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Recent Advancements and Challenges in Lignin Valorization: Green Routes towards Sustainable Bioproducts. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27186055. [PMID: 36144795 PMCID: PMC9500909 DOI: 10.3390/molecules27186055] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/10/2022] [Accepted: 09/13/2022] [Indexed: 11/27/2022]
Abstract
The aromatic hetero-polymer lignin is industrially processed in the paper/pulp and lignocellulose biorefinery, acting as a major energy source. It has been proven to be a natural resource for useful bioproducts; however, its depolymerization and conversion into high-value-added chemicals is the major challenge due to the complicated structure and heterogeneity. Conversely, the various pre-treatments techniques and valorization strategies offers a potential solution for developing a biomass-based biorefinery. Thus, the current review focus on the new isolation techniques for lignin, various pre-treatment approaches and biocatalytic methods for the synthesis of sustainable value-added products. Meanwhile, the challenges and prospective for the green synthesis of various biomolecules via utilizing the complicated hetero-polymer lignin are also discussed.
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11
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Abstract
Lignin, a rigid polymer composed of phenolic subunits with high molecular weight and complex structure, ranks behind only cellulose in the contribution to the biomass of plants. Therefore, lignin can be used as a new environmentally friendly resource for the industrial production of a variety of polymers, dyes and adhesives. Since laccase was found to be able to degrade lignin, increasing attention had been paid to the valorization of lignin. Research has mainly focused on the identification of lignin-degrading enzymes, which play a key role in lignin biodegradation, and the potential application of lignin degradation products. In this review, we describe the source, catalytic specificity and enzyme reaction mechanism of the four classes of the lignin-degrading enzymes so far discovered. In addition, the major pathways of lignin biodegradation and the applications of the degradative products are also discussed. Lignin-degrading bacteria or enzymes can be used in combination with chemical pretreatment for the production of value-added chemicals from lignin, providing a promising strategy for lignin valorization.
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Abstract
Subcellular compartmentalization is a defining feature of all cells. In prokaryotes, compartmentalization is generally achieved via protein-based strategies. The two main classes of microbial protein compartments are bacterial microcompartments and encapsulin nanocompartments. Encapsulins self-assemble into proteinaceous shells with diameters between 24 and 42 nm and are defined by the viral HK97-fold of their shell protein. Encapsulins have the ability to encapsulate dedicated cargo proteins, including ferritin-like proteins, peroxidases, and desulfurases. Encapsulation is mediated by targeting sequences present in all cargo proteins. Encapsulins are found in many bacterial and archaeal phyla and have been suggested to play roles in iron storage, stress resistance, sulfur metabolism, and natural product biosynthesis. Phylogenetic analyses indicate that they share a common ancestor with viral capsid proteins. Many pathogens encode encapsulins, and recent evidence suggests that they may contribute toward pathogenicity. The existing information on encapsulin structure, biochemistry, biological function, and biomedical relevance is reviewed here.
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Affiliation(s)
- Tobias W. Giessen
- Departments of Biomedical Engineering and Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
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13
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Atkinson E, Tuza Z, Perrino G, Stan GB, Ledesma-Amaro R. Resource-aware whole-cell model of division of labour in a microbial consortium for complex-substrate degradation. Microb Cell Fact 2022; 21:115. [PMID: 35698129 PMCID: PMC9195437 DOI: 10.1186/s12934-022-01842-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/30/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Low-cost sustainable feedstocks are essential for commercially viable biotechnologies. These feedstocks, often derived from plant or food waste, contain a multitude of different complex biomolecules which require multiple enzymes to hydrolyse and metabolise. Current standard biotechnology uses monocultures in which a single host expresses all the proteins required for the consolidated bioprocess. However, these hosts have limited capacity for expressing proteins before growth is impacted. This limitation may be overcome by utilising division of labour (DOL) in a consortium, where each member expresses a single protein of a longer degradation pathway. RESULTS Here, we model a two-strain consortium, with one strain expressing an endohydrolase and a second strain expressing an exohydrolase, for cooperative degradation of a complex substrate. Our results suggest that there is a balance between increasing expression to enhance degradation versus the burden that higher expression causes. Once a threshold of burden is reached, the consortium will consistently perform better than an equivalent single-cell monoculture. CONCLUSIONS We demonstrate that resource-aware whole-cell models can be used to predict the benefits and limitations of using consortia systems to overcome burden. Our model predicts the region of expression where DOL would be beneficial for growth on starch, which will assist in making informed design choices for this, and other, complex-substrate degradation pathways.
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Affiliation(s)
- Eliza Atkinson
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW72AZ, UK
| | - Zoltan Tuza
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW72AZ, UK
| | - Giansimone Perrino
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW72AZ, UK
| | - Guy-Bart Stan
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW72AZ, UK.
| | - Rodrigo Ledesma-Amaro
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW72AZ, UK.
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Recent advances in the treatment of lignin in papermaking wastewater. World J Microbiol Biotechnol 2022; 38:116. [PMID: 35593964 DOI: 10.1007/s11274-022-03300-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 05/04/2022] [Indexed: 10/18/2022]
Abstract
More than 695.7 million m3 of papermaking wastewater is discharged globally. It contains a mixture of complex pollutants, of which lignin is the major constituent (600-1000 mg/L) of papermaking black liquor, making it the second-largest energy-containing biomass globally and accounting for 47.4% and 59.4% of chemical oxygen demand (16,400 ± 120 mg/L) and chroma (3100 ± 22.32 mg/L) of papermaking wastewater. The complex process and dissolved pollutants are responsible for high pH, biochemical oxygen demand, chemical oxygen demand, total suspended solids, dark color, and toxicity. Papermaking wastewater has emerged as a substantial source of environmental pollution as the conventional wastewater treatment processes are high cost and seldom efficacious. This work introduces the shortcomings of the common treatment methods for papermaking wastewater and lignin, focusing on lignin biodegradation and discussing the metabolic pathways and application prospects of lignin-degrading microbial species. A comprehensive review of the existing lignin treatment methods has proposed that the reasonable amalgamation of biodegradation and various physicochemical techniques are environmentally friendly, sustainable, and economical. Lignin extraction from papermaking wastewater by technology combination is an effective approach to recover valuable organic materials and detoxify wastewater. This review focuses on recent breakthroughs and future trends in papermaking wastewater treatment and lignin removal, with special emphasis on biodegradation, recovery, and utilization of lignin, providing guidance for the mechanism exploration of lignin-degrading microorganisms and the optimization of high-value chemical production.
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15
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Wang J, Singer SD, Souto BA, Asomaning J, Ullah A, Bressler DC, Chen G. Current progress in lipid-based biofuels: Feedstocks and production technologies. BIORESOURCE TECHNOLOGY 2022; 351:127020. [PMID: 35307524 DOI: 10.1016/j.biortech.2022.127020] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 03/11/2022] [Accepted: 03/13/2022] [Indexed: 06/14/2023]
Abstract
The expanding use of fossil fuels has caused concern in terms of both energy security and environmental issues. Therefore, attempts have been made worldwide to promote the development of renewable energy sources, among which biofuel is especially attractive. Compared to other biofuels, lipid-derived biofuels have a higher energy density and better compatibility with existing infrastructure, and their performance can be readily improved by adjusting the chemical composition of lipid feedstocks. This review thus addresses the intrinsic interactions between lipid feedstocks and lipid-based biofuels, including biodiesel, and renewable equivalents to conventional gasoline, diesel, and jet fuel. Advancements in lipid-associated biofuel technology, as well as the properties and applicability of various lipid sources in terms of biofuel production, are also discussed. Furthermore, current progress in lipid production and profile optimization in the context of plant lipids, microbial lipids, and animal fats are presented to provide a wider context of lipid-based biofuel technology.
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Affiliation(s)
- Juli Wang
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada
| | - Stacy D Singer
- Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, Alberta T1J 4B1, Canada
| | - Bernardo A Souto
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada
| | - Justice Asomaning
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada
| | - Aman Ullah
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada
| | - David C Bressler
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada
| | - Guanqun Chen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
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16
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Wang H, Peng X, Li H, Giannis A, He C. Recent Biotechnology Advances in Bio-Conversion of Lignin to Lipids by Bacterial Cultures. Front Chem 2022; 10:894593. [PMID: 35494654 PMCID: PMC9039179 DOI: 10.3389/fchem.2022.894593] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 03/28/2022] [Indexed: 12/15/2022] Open
Abstract
The complexity and recalcitrance of the lignin structure is a major barrier to its efficient utilization and commercial production of high-value products. In recent years, the “bio-funneling” transformation ability of microorganisms has provided a significant opportunity for lignin conversion and integrated biorefinery. Based on the chemical structure of lignin, this mini-review introduces the recent advances of lignin depolymerization by bacterial strains and the application of microbial lignin degradation in lipids production. Furthermore, the current challenges, future trends and perspectives for microbe-based lignin conversion to lipids are discussed.
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Affiliation(s)
- Huan Wang
- State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, State-Local Joint Laboratory for Comprehensive Utilization of Biomass, Center for R&D of Fine Chemicals, Guizhou University, Guiyang, China
- Guizhou Industry Polytechnic College, Guiyang, China
| | - Xiaodong Peng
- Guizhou Institute of Products Quality Inspection and Testing, Guiyang, China
| | - Hu Li
- State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, State-Local Joint Laboratory for Comprehensive Utilization of Biomass, Center for R&D of Fine Chemicals, Guizhou University, Guiyang, China
- *Correspondence: Hu Li, ; Chao He,
| | - Apostolos Giannis
- School of Chemical and Environmental Engineering, Technical University of Crete, University Campus, Chania, Greece
| | - Chao He
- Faculty of Engineering and Natural Sciences, Tampere University, Tampere, Finland
- *Correspondence: Hu Li, ; Chao He,
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17
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Ji H, Wang L, Tao F, Yao Z, Li X, Dong C, Pang Z. A hydrotrope pretreatment for stabilized lignin extraction and high titer ethanol production. BIORESOUR BIOPROCESS 2022; 9:40. [PMID: 38647740 PMCID: PMC10992416 DOI: 10.1186/s40643-022-00530-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Accepted: 03/22/2022] [Indexed: 11/10/2022] Open
Abstract
The biomass pretreatment strategies using organic acids facilitate lignin removal and enhance the enzymatic digestion of cellulose. However, lignin always suffers a severe and irreversible condensation. The newly generated C-C bonds dramatically affect its further upgrading. In this study, we used a recyclable hydrotrope (p-Toluenessulfonic acid, p-TsOH) to dissolve lignin under mild condition and stabilized lignin with a quenching agent (formaldehyde, FA) during extraction, achieving both value-added lignin extraction and efficient enzymatic saccharification of cellulose. Approximately 63.7% of lignin was dissolved by 80% (wt. %) p-TsOH with 1.5% FA addition at 80 °C, 30 min. The obtained lignin was characterized by FTIR spectroscopy, TGA, 2D HSQC NMR spectroscopy, and GPC. The results indicated that the extracted lignin exhibited excellent properties, such as light color, a low molecular weight (Mw, 5371 g/mol), and a narrow polydispersity (Mw/Mn, 1.63). The pretreated substrate was converted to ethanol via a quasi-simultaneous saccharification and fermentation process (Q-SSF). After fermentation of 60 h, the ethanol concentration reached 38.7 ± 3.3 g/L which was equivalent to a theoretical ethanol yield of 82.9 ± 2.2% based on the glucan content, while the residual glucose concentration was only 4.69 ± 1.4 g/L. In short, this pretreatment strategy protected lignin to form new C-C linkages and improved the enzymatic saccharification of glucan for high-titer ethanol production.
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Affiliation(s)
- Hairui Ji
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue road, Jinan, 250353, China
| | - Le Wang
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue road, Jinan, 250353, China
| | - Furong Tao
- School of Chemistry and Chemical Engineering, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue road, Jinan, 250353, China
| | - Zhipeng Yao
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue road, Jinan, 250353, China
| | - Xuezhi Li
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
| | - Cuihua Dong
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue road, Jinan, 250353, China.
| | - Zhiqiang Pang
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue road, Jinan, 250353, China
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18
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Zhao ZM, Meng X, Scheidemantle B, Pu Y, Liu ZH, Li BZ, Wyman CE, Cai CM, Ragauskas AJ. Cosolvent enhanced lignocellulosic fractionation tailoring lignin chemistry and enhancing lignin bioconversion. BIORESOURCE TECHNOLOGY 2022; 347:126367. [PMID: 34801717 DOI: 10.1016/j.biortech.2021.126367] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/12/2021] [Accepted: 11/13/2021] [Indexed: 06/13/2023]
Abstract
Cosolvent Enhanced Lignocellulosic Fractionation (CELF) is an emerging solvolysis pretreatment to fractionate lignocellulosic biomass. Herein, the bioconversion performance of CELF lignin was fully evaluated for the first time. Results showed that CELF lignin possessed higher content of carboxylic acid OH, lower molecular weight, and disappeared β-O-4 and β-5 linkages compared to other two technical lignins including a conventional ethanol organosolv lignin (EOL) and a kraft lignin (KL). Rhodococcus opacus PD630 cell count from CELF lignin fermentation reached the highest value of 3.9 × 107 CFU/mL, representing a 62.5% and 77.3% improvement over EOL and KL, respectively. Correspondingly, lipid yield reached 143 mg/L from CELF lignin, which was 36.2% and 26.5% higher than from EOL and KL, respectively. Principal component analysis (PCA) revealed that more carboxylic acid groups and lower molecular weight contributed to the enhanced bioconversion performance of CELF lignin. This study demonstrates that CELF lignin is a promising candidate for bioconversion.
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Affiliation(s)
- Zhi-Min Zhao
- School of Ecology and Environment, Inner Mongolia Key Laboratory of Environmental Pollution Control & Wastes Reuse, Inner Mongolia University, Hohhot 010021, China; Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States
| | - Xianzhi Meng
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States
| | - Brent Scheidemantle
- Bourns College of Engineering-Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA 92507, United States
| | - Yunqiao Pu
- Center for Bioenergy Innovation (CBI), Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Zhi-Hua Liu
- School of Chemical Engineering and Technology, Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China
| | - Bing-Zhi Li
- School of Chemical Engineering and Technology, Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China
| | - Charles E Wyman
- Bourns College of Engineering-Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA 92507, United States
| | - Charles M Cai
- Bourns College of Engineering-Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA 92507, United States
| | - Arthur J Ragauskas
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States; Center for Bioenergy Innovation (CBI), Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Center for Renewable Carbon, Department of Forestry, Wildlife, and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, United States.
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19
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20
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Banu Jamaldheen S, Kurade MB, Basak B, Yoo CG, Oh KK, Jeon BH, Kim TH. A review on physico-chemical delignification as a pretreatment of lignocellulosic biomass for enhanced bioconversion. BIORESOURCE TECHNOLOGY 2022; 346:126591. [PMID: 34929325 DOI: 10.1016/j.biortech.2021.126591] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 12/14/2021] [Accepted: 12/16/2021] [Indexed: 06/14/2023]
Abstract
Effective pretreatment of lignocellulosic biomass (LCB) is one of the most important steps in biorefinery, ensuring the quality and commercial viability of the overall bioprocess. Lignin recalcitrance in LCB is a major bottleneck in biological conversion as the polymerization of lignin with hemicellulose hinders enzyme accessibility and further bioconversion to fuels and chemicals. Therefore, there is a need to delignify LCB to ease further bioprocessing. The efficiency of delignification, quality and quantity of the desired products, and generation of inhibitors depend upon the type of pretreatment employed. This review summarizes different single and integrated physicochemical pretreatments for delignification. Additionally, conditions required for effective delignification and the advantages and drawbacks of each method were evaluated. Advances in overcoming the recalcitrance of residual lignin to saccharification and the methods to recover lignin after delignification are also discussed. Efficient lignin recovery and valorization strategies provide an avenue for the sustainable lignocellulose biorefinery.
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Affiliation(s)
- Sumitha Banu Jamaldheen
- Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi-do 15588, Republic of Korea
| | - Mayur B Kurade
- Department of Earth Resources and Environmental Engineering, Hanyang University, 222-Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Bikram Basak
- Department of Earth Resources and Environmental Engineering, Hanyang University, 222-Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Chang Geun Yoo
- Department of Chemical Engineering, State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210, USA
| | - Kyeong Keun Oh
- Department of Chemical Engineering, Dankook University, Youngin 16890, Gyeonggi-do, Republic of Korea
| | - Byong-Hun Jeon
- Department of Earth Resources and Environmental Engineering, Hanyang University, 222-Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Tae Hyun Kim
- Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi-do 15588, Republic of Korea.
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21
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Blumenstein J, Rädisch R, Štěpánek V, Grulich M, Dostálová H, Pátek M. Identification of Rhodococcus erythropolis Promoters Controlled by Alternative Sigma Factors Using In Vivo and In Vitro Systems and Heterologous RNA Polymerase. Curr Microbiol 2022; 79:55. [PMID: 34982253 DOI: 10.1007/s00284-021-02747-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 12/10/2021] [Indexed: 11/03/2022]
Abstract
Rhodococcus erythropolis CCM2595 is a bacterial strain, which has been studied for its capability to degrade phenol and other toxic aromatic compounds. Its cell wall contains mycolic acids, which are also an attribute of other bacteria of the Mycolata group, such as Corynebacterium and Mycobacterium species. We suppose that many genes upregulated by phenol stress in R. erythropolis are controlled by the alternative sigma factors of RNA polymerase, which are active in response to the cell envelope or oxidative stress. We developed in vitro and in vivo assays to examine the connection between the stress sigma factors and genes activated by various extreme conditions, e.g., heat, cell surface, and oxidative stress. These assays are based on the procedures of such tests carried out in the related species, Corynebacterium glutamicum. We showed that the R. erythropolis CCM2595 genes frmB1 and frmB2, which encode S-formylglutathione hydrolases (named corynomycolyl transferases in C. glutamicum), are controlled by SigD, just like the homologous genes cmt1 and cmt2 in C. glutamicum. The new protocol of the in vivo and in vitro assays will enable us to classify R. erythropolis promoters according to their connection to sigma factors and to assign the genes to the corresponding sigma regulons. The complex stress responses, such as that induced by phenol, could, thus, be analyzed with respect to the gene regulation by sigma factors.
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Affiliation(s)
- Jan Blumenstein
- Institute of Microbiology of the CAS, v.v.i., Prague, Czech Republic.,Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Robert Rädisch
- Institute of Microbiology of the CAS, v.v.i., Prague, Czech Republic.,Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Václav Štěpánek
- Institute of Microbiology of the CAS, v.v.i., Prague, Czech Republic
| | - Michal Grulich
- Institute of Microbiology of the CAS, v.v.i., Prague, Czech Republic
| | - Hana Dostálová
- Institute of Microbiology of the CAS, v.v.i., Prague, Czech Republic
| | - Miroslav Pátek
- Institute of Microbiology of the CAS, v.v.i., Prague, Czech Republic.
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22
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Reshmy R, Athiyaman Balakumaran P, Divakar K, Philip E, Madhavan A, Pugazhendhi A, Sirohi R, Binod P, Kumar Awasthi M, Sindhu R. Microbial valorization of lignin: Prospects and challenges. BIORESOURCE TECHNOLOGY 2022; 344:126240. [PMID: 34737164 DOI: 10.1016/j.biortech.2021.126240] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/22/2021] [Accepted: 10/23/2021] [Indexed: 06/13/2023]
Abstract
Lignin is the world's second most prevalent biomaterial, but its effective value-added product valorization methods are still being developed. The most common preparation processes for converting lignin to platform chemicals and biofuels are fragmentation and depolymerization. Due to its structural diversity, fragmentation generally produces a variety of products, necessitating tedious separation and purifying methods to isolate the desired products. Bacterial-based techniques are commonly utilized for lignin fragmentation due to their high metabolitic activity. Recent advancements in lignin valorization utilizing bacteria, such as lignin decomposing microbes and major pathways involved that can breakdown lignin into various valuable products namely lipids, furfural, vanillin, polyhydroxybutyrate, poly lactic acid blends were discussed in this review. This review also covers the genetic and fermentation methodologies to enhance lignin decomposition, challenges and future trends of microbe based lignin valorization.
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Affiliation(s)
- R Reshmy
- Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara 690 110, Kerala, India
| | - Palanisamy Athiyaman Balakumaran
- Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695 019, Kerala, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002, India
| | - K Divakar
- Department of Biotechnology, Sri Venkateswara College of Engineering, Sriperumbudur 602 117, Tamil Nadu, India
| | - Eapen Philip
- Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara 690 110, Kerala, India
| | - Aravind Madhavan
- Rajiv Gandhi Centre for Biotechnology, Jagathy, Thiruvananthapuram 695 014, Kerala, India
| | - Arivalagan Pugazhendhi
- School of Renewable Energy, Maejo University, Chiang Mai 50290, Thailand; College of Medical and Health Science, Asia University, Taichung, Taiwan
| | - Ranjna Sirohi
- Department of Chemical & Biological Engineering, Korea University, Seoul 136713, Republic of Korea; Centre for Energy and Environmental Sustainability, Lucknow 226 029, Uttar Pradesh, India
| | - Parameswaran Binod
- Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695 019, Kerala, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002, India
| | - Mukesh Kumar Awasthi
- College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi 712 100, China
| | - Raveendran Sindhu
- Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695 019, Kerala, India.
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23
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Weiland F, Kohlstedt M, Wittmann C. Guiding stars to the field of dreams: Metabolically engineered pathways and microbial platforms for a sustainable lignin-based industry. Metab Eng 2021; 71:13-41. [PMID: 34864214 DOI: 10.1016/j.ymben.2021.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/25/2021] [Accepted: 11/29/2021] [Indexed: 12/19/2022]
Abstract
Lignin is an important structural component of terrestrial plants and is readily generated during biomass fractionation in lignocellulose processing facilities. Due to lacking alternatives the majority of technical lignins is industrially simply burned into heat and energy. However, regarding its vast abundance and a chemically interesting richness in aromatics, lignin is presently regarded as the most under-utilized and promising feedstock for value-added applications. Notably, microbes have evolved powerful enzymes and pathways that break down lignin and metabolize its various aromatic components. This natural pathway atlas meanwhile serves as a guiding star for metabolic engineers to breed designed cell factories and efficiently upgrade this global waste stream. The metabolism of aromatic compounds, in combination with success stories from systems metabolic engineering, as reviewed here, promises a sustainable product portfolio from lignin, comprising bulk and specialty chemicals, biomaterials, and fuels.
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Affiliation(s)
- Fabia Weiland
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Michael Kohlstedt
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Christoph Wittmann
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany.
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24
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Azubuike CC, Allemann MN, Michener JK. Microbial assimilation of lignin-derived aromatic compounds and conversion to value-added products. Curr Opin Microbiol 2021; 65:64-72. [PMID: 34775172 DOI: 10.1016/j.mib.2021.10.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 11/03/2022]
Abstract
Lignin is an abundant and sustainable source of aromatic compounds that can be converted to value-added products. However, lignin is underutilized, since depolymerization produces a complex mixture of aromatic compounds that is difficult to convert to a single product. Microbial conversion of mixed aromatic substrates provides a potential solution to this conversion challenge. Recent advances have expanded the range of lignin-derived aromatic substrates that can be assimilated and demonstrated efficient conversion via central metabolism to new potential products. The development of additional non-model microbial hosts and genetic tools for these hosts have accelerated engineering efforts. However, yields with real depolymerized lignin are still low, and additional work will be required to achieve viable conversion processes.
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Affiliation(s)
| | - Marco N Allemann
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Joshua K Michener
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA.
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25
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Cai C, Xu Z, Zhou H, Chen S, Jin M. Valorization of lignin components into gallate by integrated biological hydroxylation, O-demethylation, and aryl side-chain oxidation. SCIENCE ADVANCES 2021; 7:eabg4585. [PMID: 34516898 PMCID: PMC8442903 DOI: 10.1126/sciadv.abg4585] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Converting lignin components into a single product is a promising way to upgrade lignin. Here, an efficient biocatalyst was developed to selectively produce gallate from lignin components by integrating three main reactions: hydroxylation, O-demethylation, and aryl side-chain oxidation. A rationally designed hydroxylase system was first introduced into a gallate biodegradation pathway–blocked Rhodococcus opacus mutant so that gallate accumulated from protocatechuate and compounds in its upper pathways. Native and heterologous O-demethylation systems were then used, leading to multiple lignin-derived methoxy aromatics being converted to gallate. Furthermore, an aryl side-chain oxidase was engaged to broaden the substrate spectrum. Consequently, the developed biocatalyst showed that gallate yields as high as 0.407 and 0.630 g of gallate per gram of lignin when alkaline-pretreated lignin and base-depolymerized ammonia fiber explosion lignin were applied as substrates, respectively. These results suggested that this rationally developed biocatalyst enabled the lignin valorization process to be simple and efficient.
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Affiliation(s)
- Chenggu Cai
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Zhaoxian Xu
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Huarong Zhou
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Sitong Chen
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Mingjie Jin
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
- Corresponding author.
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26
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Sethupathy S, Morales GM, Li Y, Wang Y, Jiang J, Sun J, Zhu D. Harnessing microbial wealth for lignocellulose biomass valorization through secretomics: a review. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:154. [PMID: 34225772 PMCID: PMC8256616 DOI: 10.1186/s13068-021-02006-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/26/2021] [Indexed: 05/10/2023]
Abstract
The recalcitrance of lignocellulosic biomass is a major constraint to its high-value use at industrial scale. In nature, microbes play a crucial role in biomass degradation, nutrient recycling and ecosystem functioning. Therefore, the use of microbes is an attractive way to transform biomass to produce clean energy and high-value compounds. The microbial degradation of lignocelluloses is a complex process which is dependent upon multiple secreted enzymes and their synergistic activities. The availability of the cutting edge proteomics and highly sensitive mass spectrometry tools make possible for researchers to probe the secretome of microbes and microbial consortia grown on different lignocelluloses for the identification of hydrolytic enzymes of industrial interest and their substrate-dependent expression. This review summarizes the role of secretomics in identifying enzymes involved in lignocelluloses deconstruction, the development of enzyme cocktails and the construction of synthetic microbial consortia for biomass valorization, providing our perspectives to address the current challenges.
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Affiliation(s)
- Sivasamy Sethupathy
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Gabriel Murillo Morales
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Yixuan Li
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Yongli Wang
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Jianxiong Jiang
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Jianzhong Sun
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Daochen Zhu
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
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DeLorenzo DM, Diao J, Carr R, Hu Y, Moon TS. An Improved CRISPR Interference Tool to Engineer Rhodococcus opacus. ACS Synth Biol 2021; 10:786-798. [PMID: 33787248 DOI: 10.1021/acssynbio.0c00591] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rhodococcus opacus is a nonmodel bacterium that is well suited for valorizing lignin. Despite recent advances in our systems-level understanding of its versatile metabolism, studies of its gene functions at a single gene level are still lagging. Elucidating gene functions in nonmodel organisms is challenging due to limited genetic engineering tools that are convenient to use. To address this issue, we developed a simple gene repression system based on CRISPR interference (CRISPRi). This gene repression system uses a T7 RNA polymerase system to express a small guide RNA, demonstrating improved repression compared to the previously demonstrated CRISPRi system (i.e., the maximum repression efficiency improved from 58% to 85%). Additionally, our cloning strategy allows for building multiple CRISPRi plasmids in parallel without any PCR step, facilitating the engineering of this GC-rich organism. Using the improved CRISPRi system, we confirmed the annotated roles of four metabolic pathway genes, which had been identified by our previous transcriptomic analysis to be related to the consumption of benzoate, vanillate, catechol, and acetate. Furthermore, we showed our tool's utility by demonstrating the inducible accumulation of muconate that is a precursor of adipic acid, an important monomer for nylon production. While the maximum muconate yield obtained using our tool was 30% of the yield obtained using gene knockout, our tool showed its inducibility and partial repressibility. Our CRISPRi tool will be useful to facilitate functional studies of this nonmodel organism and engineer this promising microbial chassis for lignin valorization.
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Affiliation(s)
- Drew M. DeLorenzo
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Jinjin Diao
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Rhiannon Carr
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Yifeng Hu
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Tae Seok Moon
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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Sivagurunathan P, Raj T, Mohanta CS, Semwal S, Satlewal A, Gupta RP, Puri SK, Ramakumar SSV, Kumar R. 2G waste lignin to fuel and high value-added chemicals: Approaches, challenges and future outlook for sustainable development. CHEMOSPHERE 2021; 268:129326. [PMID: 33360003 DOI: 10.1016/j.chemosphere.2020.129326] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 12/01/2020] [Accepted: 12/13/2020] [Indexed: 06/12/2023]
Abstract
Lignin is produced as a byproduct in cellulosic biorefinery as well in pulp and paper industries and has the potential for the synthesis of a variety of phenolics chemicals, biodegradable polymers, and high value-added chemicals surrogate to conventional petro-based fuels. Therefore, in this critical review, we emphasize the possible scenario for lignin isolation, transformation into value addition chemicals/materials for the economic viability of current biorefineries. Additionally, this review covers the chemical structure of lignocellulosic biomass/lignin, worldwide availability of lignin and describe various thermochemical (homogeneous/heterogeneous base/acid-catalyzed depolymerization, oxidative, hydrogenolysis etc.) and biotechnological developments for the production of bio-based low molecular weight phenolics, i.e. polyhydroxyalkanoates, vanillin, adipic acid, lipids etc. Besides, some functional chemicals applications, lignin-formaldehyde ion exchange resin, electrochemical and production of few targeted chemicals are also elaborated. Finally, we examine the challenges, opportunities and prospects way forward related to lignin valorization.
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Affiliation(s)
- P Sivagurunathan
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Tirath Raj
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Chandra Sekhar Mohanta
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Surbhi Semwal
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Alok Satlewal
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Ravi P Gupta
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Suresh K Puri
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - S S V Ramakumar
- Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India
| | - Ravindra Kumar
- DBT- IOC Advanced Bio Energy Research Center, Indian Oil Corporation Ltd. Research and Development Centre, Sector-13, Faridabad, Haryana, 121007, India.
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29
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Pátek M, Grulich M, Nešvera J. Stress response in Rhodococcus strains. Biotechnol Adv 2021; 53:107698. [PMID: 33515672 DOI: 10.1016/j.biotechadv.2021.107698] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 01/13/2021] [Accepted: 01/15/2021] [Indexed: 12/13/2022]
Abstract
Rhodococci are bacteria which can survive under various extreme conditions, in the presence of toxic compounds, and in other hostile habitats. Their tolerance of unfavorable conditions is associated with the structure of their cell wall and their large array of enzymes, which degrade or detoxify harmful compounds. Their physiological and biotechnological properties, together with tools for their genetic manipulation, enable us to apply them in biotransformations, biodegradation and bioremediation. Many such biotechnological applications cause stresses that positively or negatively affect their efficiency. Whereas numerous reviews on rhodococci described their enzyme activities, the optimization of degradation or production processes, and corresponding technological solutions, only a few reviews discussed some specific effects of stresses on the physiology of rhodococci and biotechnological processes. This review aims to comprehensively describe individual stress responses in Rhodococcus strains, the interconnection of different types of stresses and their consequences for cell physiology. We examine here the responses to (1) environmental stresses (desiccation, heat, cold, osmotic and pH stress), (2) the presence of stress-inducing compounds (metals, organic compounds and antibiotics) in the environment (3) starvation and (4) stresses encountered during biotechnological applications. Adaptations of the cell envelope, the formation of multicellular structures and stresses induced by the interactions of hosts with pathogenic rhodococci are also included. The roles of sigma factors of RNA polymerase in the global regulation of stress responses in rhodococci are described as well. Although the review covers a large number of stressful conditions, our intention was to provide an overview of the selected stress responses and their possible connection to biotechnological processes, not an exhaustive survey of the scientific literature. The findings on stress responses summarized in this review and the demonstration of gaps in current knowledge may motivate researchers working to fill these gaps.
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Affiliation(s)
- Miroslav Pátek
- Institute of Microbiology of the CAS, v. v. i., Prague, Czech Republic.
| | - Michal Grulich
- Institute of Microbiology of the CAS, v. v. i., Prague, Czech Republic.
| | - Jan Nešvera
- Institute of Microbiology of the CAS, v. v. i., Prague, Czech Republic.
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30
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Xu Z, Pan C, Li X, Hao N, Zhang T, Gaffrey MJ, Pu Y, Cort JR, Ragauskas AJ, Qian WJ, Yang B. Enhancement of polyhydroxyalkanoate production by co-feeding lignin derivatives with glycerol in Pseudomonas putida KT2440. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:11. [PMID: 33413621 PMCID: PMC7792162 DOI: 10.1186/s13068-020-01861-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/17/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND Efficient utilization of all available carbons from lignocellulosic biomass is critical for economic efficiency of a bioconversion process to produce renewable bioproducts. However, the metabolic responses that enable Pseudomonas putida to utilize mixed carbon sources to generate reducing power and polyhydroxyalkanoate (PHA) remain unclear. Previous research has mainly focused on different fermentation strategies, including the sequential feeding of xylose as the growth stage substrate and octanoic acid as the PHA-producing substrate, feeding glycerol as the sole carbon substrate, and co-feeding of lignin and glucose. This study developed a new strategy-co-feeding glycerol and lignin derivatives such as benzoate, vanillin, and vanillic acid in Pseudomonas putida KT2440-for the first time, which simultaneously improved both cell biomass and PHA production. RESULTS Co-feeding lignin derivatives (i.e. benzoate, vanillin, and vanillic acid) and glycerol to P. putida KT2440 was shown for the first time to simultaneously increase cell dry weight (CDW) by 9.4-16.1% and PHA content by 29.0-63.2%, respectively, compared with feeding glycerol alone. GC-MS results revealed that the addition of lignin derivatives to glycerol decreased the distribution of long-chain monomers (C10 and C12) by 0.4-4.4% and increased the distribution of short-chain monomers (C6 and C8) by 0.8-3.5%. The 1H-13C HMBC, 1H-13C HSQC, and 1H-1H COSY NMR analysis confirmed that the PHA monomers (C6-C14) were produced when glycerol was fed to the bacteria alone or together with lignin derivatives. Moreover, investigation of the glycerol/benzoate/nitrogen ratios showed that benzoate acted as an independent factor in PHA synthesis. Furthermore, 1H, 13C and 31P NMR metabolite analysis and mass spectrometry-based quantitative proteomics measurements suggested that the addition of benzoate stimulated oxidative-stress responses, enhanced glycerol consumption, and altered the intracellular NAD+/NADH and NADPH/NADP+ ratios by up-regulating the proteins involved in energy generation and storage processes, including the Entner-Doudoroff (ED) pathway, the reductive TCA route, trehalose degradation, fatty acid β-oxidation, and PHA biosynthesis. CONCLUSIONS This work demonstrated an effective co-carbon feeding strategy to improve PHA content/yield and convert lignin derivatives into value-added products in P. putida KT2440. Co-feeding lignin break-down products with other carbon sources, such as glycerol, has been demonstrated as an efficient way to utilize biomass to increase PHA production in P. putida KT2440. Moreover, the involvement of aromatic degradation favours further lignin utilization, and the combination of proteomics and metabolomics with NMR sheds light on the metabolic and regulatory mechanisms for cellular redox balance and potential genetic targets for a higher biomass carbon conversion efficiency.
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Affiliation(s)
- Zhangyang Xu
- Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA
| | - Chunmei Pan
- Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA
- College of Food and Bioengineering, Henan University of Animal Husbandry and Economy, Zhengzhou, 450046, Henan, China
| | - Xiaolu Li
- Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA
| | - Naijia Hao
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996, USA
| | - Tong Zhang
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Matthew J Gaffrey
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Yunqiao Pu
- Joint Institute for Biological Sciences, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - John R Cort
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Arthur J Ragauskas
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996, USA
- Joint Institute for Biological Sciences, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, University of Tennessee Institute of Agriculture, Knoxville, TN, 37996, USA
| | - Wei-Jun Qian
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Bin Yang
- Bioproducts, Sciences & Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA, 99354, USA.
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
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31
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Kumar M, You S, Beiyuan J, Luo G, Gupta J, Kumar S, Singh L, Zhang S, Tsang DCW. Lignin valorization by bacterial genus Pseudomonas: State-of-the-art review and prospects. BIORESOURCE TECHNOLOGY 2021; 320:124412. [PMID: 33249259 DOI: 10.1016/j.biortech.2020.124412] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 11/08/2020] [Accepted: 11/11/2020] [Indexed: 06/12/2023]
Abstract
The most prominent aromatic feedstock on Earth is lignin, however, lignin valorization is still an underrated subject. The principal preparatory strategies for lignin valorization are fragmentation and depolymerization which help in the production of fuels and chemicals. Owing to lignin's structural heterogeneity, these strategies result in product generation which requires tedious separation and purification to extract target products. The bacterial genus Pseudomonas has been dominant for its lignin valorization potency, owing to a robust enzymatic machinery that is used to funnel variable lignin derivatives into certain target products such as polyhydroxyalkanotes (PHAs) and cis, cis-muconic acid (MA). In this review, the potential of genus Pseudomonas in lignin valorization is critically reviewed along with the advanced genetic techniques and tools to ease the use of lignin/lignin-model compounds for the synthesis of bioproducts. This review also highlights the research gaps in lignin biovalorization and discuss the challenges and possibilities for future research.
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Affiliation(s)
- Manish Kumar
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; CSIR - National Environmental and Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India
| | - Siming You
- University of Glasgow, James Watt School of Engineering, Glasgow G12 8 QQ, United Kingdom
| | - Jingzi Beiyuan
- Biochar Engineering Technology Research Center of Guangdong Province, School of Environment and Chemical Engineering, Foshan University, Foshan 528000, China
| | - Gang Luo
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Juhi Gupta
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sunil Kumar
- CSIR - National Environmental and Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India
| | - Lal Singh
- CSIR - National Environmental and Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India
| | - Shicheng Zhang
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Daniel C W Tsang
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
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32
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Zhao ZM, Liu ZH, Pu Y, Meng X, Xu J, Yuan JS, Ragauskas AJ. Emerging Strategies for Modifying Lignin Chemistry to Enhance Biological Lignin Valorization. CHEMSUSCHEM 2020; 13:5423-5432. [PMID: 32750220 DOI: 10.1002/cssc.202001401] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 07/19/2020] [Indexed: 06/11/2023]
Abstract
Biological lignin valorization represents a promising approach contributing to sustainable and economic biorefineries. The low level of valuable lignin-derived products remains a major challenge hindering the implementation of microbial lignin conversion. Lignin's properties play a significant role in determining the efficiency of lignin bioconversion. To date, despite significant progress in the development of biomass pretreatment, lignin fractionation, and fermentation over the last few decades, little efforts have gone into identifying the ideal lignin substrates for an efficient microbial metabolism. In this Minireview, emerging and state-of-the-art strategies for biomass pretreatment and lignin fractionation are summarized to elaborate their roles in modifying lignin structure for bioconversion. Fermentation strategies aimed at enhancing lignin depolymerization for microbial utilization are systematically reviewed as well. With an improved understanding of the ideal lignin structure elucidated by comprehensive metabolic pathways and/or big data analysis, modifying lignin chemistry could be more directional and effective. Ultimately, together with the progress of fermentation process optimization, biological lignin valorization will become more competitive in biorefineries.
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Affiliation(s)
- Zhi-Min Zhao
- School of Ecology and Environment, Inner Mongolia Key Laboratory of Environmental Pollution Controlling and Wastes Recycling, Inner Mongolia University, Hohhot, 010021, P. R. China
- Department of Chemical & Biomolecular Engineering, University of Tennessee Knoxville, Knoxville, TN 37996, USA
| | - Zhi-Hua Liu
- Synthetic and Systems Biology Innovation Hub (SSBiH), Texas A&M University, College Station, TX 77843, USA
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA
| | - Yunqiao Pu
- Center for Bioenergy Innovation, Joint Institute of Biological Science, Biosciences Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA
| | - Xianzhi Meng
- Department of Chemical & Biomolecular Engineering, University of Tennessee Knoxville, Knoxville, TN 37996, USA
| | - Jifei Xu
- School of Ecology and Environment, Inner Mongolia Key Laboratory of Environmental Pollution Controlling and Wastes Recycling, Inner Mongolia University, Hohhot, 010021, P. R. China
| | - Joshua S Yuan
- Synthetic and Systems Biology Innovation Hub (SSBiH), Texas A&M University, College Station, TX 77843, USA
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA
| | - Arthur J Ragauskas
- Department of Chemical & Biomolecular Engineering, University of Tennessee Knoxville, Knoxville, TN 37996, USA
- Center for Bioenergy Innovation, Joint Institute of Biological Science, Biosciences Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA
- Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, USA
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33
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Cho IJ, Choi KR, Lee SY. Microbial production of fatty acids and derivative chemicals. Curr Opin Biotechnol 2020; 65:129-141. [DOI: 10.1016/j.copbio.2020.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 02/14/2020] [Accepted: 02/14/2020] [Indexed: 12/11/2022]
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34
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Hu P, Li H, Xiao W, Xie X, Yang Y, Duan L, Zhou S, Hu Y, Qiao Q, Ran Q, Jiang Z. Effect of Rhodococcus sp. pretreatment on cellulose hydrolysis of corn stalk. Prep Biochem Biotechnol 2020; 51:137-143. [PMID: 32755478 DOI: 10.1080/10826068.2020.1799391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Pretreatment can improve the hydrolysis efficiency of cellulose, in which biological pretreatment plays an important role. In the present study, we uncovered that Rhodococcus has the ability of lignin degradation, which can decompose lignin and serve as a carbon source to meet the needs of its own growth. We used Rhodococcus to pretreat the corn stalks and evaluate the effect on cellulose hydrolysis. The concentration of reducing sugar produced by the hydrolysis of corn stalk after pretreatment of Rhodococcus is 2.95 g/L. SEM imaging showed that Rhodococcus pretreatment resulted the surface of corn stalk to be no longer complete, some lamellar structures fall off, and leave obvious traces, and obvious delamination was found at the edge of the fault. AFM imaging showed that the pretreatment changed the lignin structure of the corn stalk material surface, resulting in a higher surface roughness of 9.37. These results indicated that Rhodococcus pretreatment can improve the saccharification efficiency of cellulose by removing lignin and increasing the surface roughness of the material.
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Affiliation(s)
- Pan Hu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Huanan Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Wenjing Xiao
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Xiaohang Xie
- Hubei Key Laboratory of Regional Development and Environmental Response, College of Resources and Environmental Science, Hubei University, Wuhan, China
| | - Yuxian Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Lei Duan
- Wuhan SunHY Biological Co., Ltd., Wuhan, China
| | - Shanna Zhou
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Yanmei Hu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Qiming Qiao
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Qiuping Ran
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
| | - Zhengbing Jiang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China.,Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan, China
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35
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Chatterjee A, DeLorenzo DM, Carr R, Moon TS. Bioconversion of renewable feedstocks by Rhodococcus opacus. Curr Opin Biotechnol 2020; 64:10-16. [DOI: 10.1016/j.copbio.2019.08.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 08/19/2019] [Accepted: 08/25/2019] [Indexed: 12/18/2022]
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36
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Tailoring microbes to upgrade lignin. Curr Opin Chem Biol 2020; 59:23-29. [PMID: 32388219 DOI: 10.1016/j.cbpa.2020.04.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 03/31/2020] [Accepted: 04/01/2020] [Indexed: 12/16/2022]
Abstract
Lignin depolymerization generates a mixture of numerous compounds that are difficult to separate cost-effectively. To address this heterogeneity issue, microbes have been employed to 'biologically funnel' a broad range of compounds present in depolymerized lignin into common central metabolites that can be converted into a single desirable product. Because the composition of depolymerized lignin varies significantly with the type of biomass and the depolymerization method, microbes should be selected and engineered by considering this compositional variation. An ideal microbe must efficiently metabolize all relevant lignin-derived compounds regardless of the compositional variation of feedstocks, but discovering or developing such a perfect microbe is very challenging. Instead, developing multiple tailored microbes to tolerate a given mixture of lignin-derived compounds and to convert most of these into a target product is more practical. This review summarizes recent progress toward the development of such microbes for lignin valorization and offers future directions.
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37
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Outer membrane vesicles catabolize lignin-derived aromatic compounds in Pseudomonas putida KT2440. Proc Natl Acad Sci U S A 2020; 117:9302-9310. [PMID: 32245809 DOI: 10.1073/pnas.1921073117] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Lignin is an abundant and recalcitrant component of plant cell walls. While lignin degradation in nature is typically attributed to fungi, growing evidence suggests that bacteria also catabolize this complex biopolymer. However, the spatiotemporal mechanisms for lignin catabolism remain unclear. Improved understanding of this biological process would aid in our collective knowledge of both carbon cycling and microbial strategies to valorize lignin to value-added compounds. Here, we examine lignin modifications and the exoproteome of three aromatic-catabolic bacteria: Pseudomonas putida KT2440, Rhodoccocus jostii RHA1, and Amycolatopsis sp. ATCC 39116. P. putida cultivation in lignin-rich media is characterized by an abundant exoproteome that is dynamically and selectively packaged into outer membrane vesicles (OMVs). Interestingly, many enzymes known to exhibit activity toward lignin-derived aromatic compounds are enriched in OMVs from early to late stationary phase, corresponding to the shift from bioavailable carbon to oligomeric lignin as a carbon source. In vivo and in vitro experiments demonstrate that enzymes contained in the OMVs are active and catabolize aromatic compounds. Taken together, this work supports OMV-mediated catabolism of lignin-derived aromatic compounds as an extracellular strategy for nutrient acquisition by soil bacteria and suggests that OMVs could potentially be useful tools for synthetic biology and biotechnological applications.
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38
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Li C, Chen C, Wu X, Tsang CW, Mou J, Yan J, Liu Y, Lin CSK. Recent advancement in lignin biorefinery: With special focus on enzymatic degradation and valorization. BIORESOURCE TECHNOLOGY 2019; 291:121898. [PMID: 31395402 DOI: 10.1016/j.biortech.2019.121898] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/22/2019] [Accepted: 07/23/2019] [Indexed: 05/07/2023]
Abstract
With the intensive development of lignocellulosic biorefineries to produce fuels and chemicals from biomass-derived carbohydrates, lignin was generated at a large quantity every year. Therefore, lignin has received increasing attention as an abundant aromatics resource in terms of research and development efforts for value-added chemicals production. In this review, studies about lignin degradation especially the crucial enzymes involved and the reaction mechanism were substantially discussed, which provided the molecular basis of lignin biodegradation. Then, the latest improvements in lignin valorization by biological methods were summarized and case studies about value-added compounds from lignin were introduced. Afterwards, challenges, opportunities and prospects regarding biorefinery of lignin were presented.
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Affiliation(s)
- Chong Li
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, Guangdong 518120, People's Republic of China
| | - Chao Chen
- BioZone, Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON M5S 3E5, Canada
| | - Xiaofen Wu
- Hunan Institute of Nuclear Agricultural Science and Space Breeding, Hunan Academy of Agricultural Sciences, Changsha, Hunan 410125, People's Republic of China
| | - Chi-Wing Tsang
- Faculty of Science and Technology, Technological and Higher Education Institute of Hong Kong, Hong Kong, China
| | - Jinhua Mou
- School of Energy and Environment, City University of Hong Kong, Hong Kong
| | - Jianbin Yan
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, Guangdong 518120, People's Republic of China
| | - Yun Liu
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Carol Sze Ki Lin
- School of Energy and Environment, City University of Hong Kong, Hong Kong.
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Bhatia SK, Gurav R, Choi TR, Han YH, Park YL, Park JY, Jung HR, Yang SY, Song HS, Kim SH, Choi KY, Yang YH. Bioconversion of barley straw lignin into biodiesel using Rhodococcus sp. YHY01. BIORESOURCE TECHNOLOGY 2019; 289:121704. [PMID: 31276990 DOI: 10.1016/j.biortech.2019.121704] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 06/24/2019] [Accepted: 06/25/2019] [Indexed: 06/09/2023]
Abstract
Rhodococcus sp. YHY01 was studied to utilize various lignin derived aromatic compounds. It was able to utilize p-coumaric acid, cresol, and 2,6 dimethoxyphenol and resulted in biomass production i.e. 0.38 g dcw/L, 0.25 g dcw/L and 0.1 g dcw/L, and lipid accumulation i.e. 49%, 40%, 30%, respectively. The half maximal inhibitory concentration (IC50) value for p-coumaric acid (13.4 mM), cresol (7.9 mM), and 2,6 dimethoxyphenol (3.4 mM) was analyzed. Dimethyl sulfoxide (DMSO) solubilized barley straw lignin fraction was used as a carbon source for Rhodococcus sp. YHY01 and resulted in 0.130 g dcw/L with 39% w/w lipid accumulation. Major fatty acids were palmitic acid (C16:0) 51.87%, palmitoleic acid (C16:l) 14.90%, and oleic acid (C18:1) 13.76%, respectively. Properties of biodiesel produced from barley straw lignin were as iodine value (IV) 27.25, cetane number (CN) 65.57, cold filter plugging point (CFPP) 14.36, viscosity (υ) 3.81, and density (ρ) 0.86.
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Affiliation(s)
- Shashi Kant Bhatia
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea; Institute for Ubiquitous Information Technology and App1ications (CBRU), Konkuk University, Seoul, South Korea
| | - Ranjit Gurav
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Tae-Rim Choi
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Yeong Hoon Han
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Ye-Lim Park
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Jun Young Park
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Hye-Rim Jung
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Soo-Yeon Yang
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Hun-Suk Song
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea
| | - Sang-Hyoun Kim
- School of Civil and Environmental Engineering, Yonsei University, Seoul, South Korea
| | - Kwon-Young Choi
- Department of Environmental Engineering, Ajou University, Suwon, Gyeonggi-do, South Korea
| | - Yung-Hun Yang
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea; Institute for Ubiquitous Information Technology and App1ications (CBRU), Konkuk University, Seoul, South Korea.
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40
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Xiang H, Sun-Waterhouse D, Waterhouse GI, Cui C, Ruan Z. Fermentation-enabled wellness foods: A fresh perspective. FOOD SCIENCE AND HUMAN WELLNESS 2019. [DOI: 10.1016/j.fshw.2019.08.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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41
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Anthony WE, Carr RR, DeLorenzo DM, Campbell TP, Shang Z, Foston M, Moon TS, Dantas G. Development of Rhodococcus opacus as a chassis for lignin valorization and bioproduction of high-value compounds. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:192. [PMID: 31404385 PMCID: PMC6683499 DOI: 10.1186/s13068-019-1535-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 07/24/2019] [Indexed: 05/09/2023]
Abstract
The current extraction and use of fossil fuels has been linked to extensive negative health and environmental outcomes. Lignocellulosic biomass-derived biofuels and bioproducts are being actively considered as renewable alternatives to the fuels, chemicals, and materials produced from fossil fuels. A major challenge limiting large-scale, economic deployment of second-generation biorefineries is the insufficient product yield, diversity, and value that current conversion technologies can extract from lignocellulose, in particular from the underutilized lignin fraction. Rhodococcus opacus PD630 is an oleaginous gram-positive bacterium with innate catabolic pathways and tolerance mechanisms for the inhibitory aromatic compounds found in depolymerized lignin, as well as native or engineered pathways for hexose and pentose sugars found in the carbohydrate fractions of biomass. As a result, R. opacus holds potential as a biological chassis for the conversion of lignocellulosic biomass into biodiesel precursors and other value-added products. This review begins by examining the important role that lignin utilization will play in the future of biorefineries and by providing a concise survey of the current lignin conversion technologies. The genetic machinery and capabilities of R. opacus that allow the bacterium to tolerate and metabolize aromatic compounds and depolymerized lignin are also discussed, along with a synopsis of the genetic toolbox and synthetic biology methods now available for engineering this organism. Finally, we summarize the different feedstocks that R. opacus has been demonstrated to consume, and the high-value products that it has been shown to produce. Engineered R. opacus will enable lignin valorization over the coming years, leading to cost-effective conversion of lignocellulose into fuels, chemicals, and materials.
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Affiliation(s)
- Winston E. Anthony
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110 USA
| | - Rhiannon R. Carr
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Drew M. DeLorenzo
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Tayte P. Campbell
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110 USA
| | - Zeyu Shang
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Marcus Foston
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Tae Seok Moon
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Gautam Dantas
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110 USA
- Department of Pathology and Immunology, Washington University in St. Louis School of Medicine, St. Louis, MO 63108 USA
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
- Department of Molecular Microbiology, Washington University in St. Louis School of Medicine, St. Louis, MO 63108 USA
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