1
|
Cha M, Kim JK, Lee WH, Song H, Lee TG, Kim SK, Kim SJ. Metabolic engineering of Caldicellulosiruptor bescii for hydrogen production. Appl Microbiol Biotechnol 2024; 108:65. [PMID: 38194138 PMCID: PMC10776719 DOI: 10.1007/s00253-023-12974-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 12/04/2023] [Accepted: 12/15/2023] [Indexed: 01/10/2024]
Abstract
Hydrogen is an alternative fuel for transportation vehicles because it is clean, sustainable, and highly flammable. However, the production of hydrogen from lignocellulosic biomass by microorganisms presents challenges. This microbial process involves multiple complex steps, including thermal, chemical, and mechanical treatment of biomass to remove hemicellulose and lignin, as well as enzymatic hydrolysis to solubilize the plant cell walls. These steps not only incur costs but also result in the production of toxic hydrolysates, which inhibit microbial growth. A hyper-thermophilic bacterium of Caldicellulosiruptor bescii can produce hydrogen by decomposing and fermenting plant biomass without the need for conventional pretreatment. It is considered as a consolidated bioprocessing (CBP) microorganism. This review summarizes the basic scientific knowledge and hydrogen-producing capacity of C. bescii. Its genetic system and metabolic engineering strategies to improve hydrogen production are also discussed. KEY POINTS: • Hydrogen is an alternative and eco-friendly fuel. • Caldicellulosiruptor bescii produces hydrogen with a high yield in nature. • Metabolic engineering can make C. bescii to improve hydrogen production.
Collapse
Affiliation(s)
- Minseok Cha
- Research Center for Biological Cybernetics, Chonnam National University, Gwangju, 61186, Republic of Korea
| | - Jung Kon Kim
- Department of Animal Environment, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Won-Heong Lee
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Republic of Korea
| | | | - Tae-Gi Lee
- Department of Food Science and Biotechnology, Chung-Ang University, Gyeonggi, 17546, Republic of Korea
| | - Sun-Ki Kim
- Department of Food Science and Biotechnology, Chung-Ang University, Gyeonggi, 17546, Republic of Korea
| | - Soo-Jung Kim
- Research Center for Biological Cybernetics, Chonnam National University, Gwangju, 61186, Republic of Korea.
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Republic of Korea.
| |
Collapse
|
2
|
Tanwee TNN, Lipscomb GL, Vailionis JL, Zhang K, Bing RG, O'Quinn HC, Poole FL, Zhang Y, Kelly RM, Adams MWW. Metabolic engineering of Caldicellulosiruptor bescii for 2,3-butanediol production from unpretreated lignocellulosic biomass and metabolic strategies for improving yields and titers. Appl Environ Microbiol 2024; 90:e0195123. [PMID: 38131671 PMCID: PMC10807448 DOI: 10.1128/aem.01951-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 11/21/2023] [Indexed: 12/23/2023] Open
Abstract
The platform chemical 2,3-butanediol (2,3-BDO) is used to derive products, such as 1,3-butadiene and methyl ethyl ketone, for the chemical and fuel production industries. Efficient microbial 2,3-BDO production at industrial scales has not been achieved yet for various reasons, including product inhibition to host organisms, mixed stereospecificity in product formation, and dependence on expensive substrates (i.e., glucose). In this study, we explore engineering of a 2,3-BDO pathway in Caldicellulosiruptor bescii, an extremely thermophilic (optimal growth temperature = 78°C) and anaerobic bacterium that can break down crystalline cellulose and hemicellulose into fermentable C5 and C6 sugars. In addition, C. bescii grows on unpretreated plant biomass, such as switchgrass. Biosynthesis of 2,3-BDO involves three steps: two molecules of pyruvate are condensed into acetolactate; acetolactate is decarboxylated to acetoin, and finally, acetoin is reduced to 2,3-BDO. C. bescii natively produces acetoin; therefore, in order to complete the 2,3-BDO biosynthetic pathway, C. bescii was engineered to produce a secondary alcohol dehydrogenase (sADH) to catalyze the final step. Two previously characterized, thermostable sADH enzymes with high affinity for acetoin, one from a bacterium and one from an archaeon, were tested independently. When either sADH was present in C. bescii, the recombinant strains were able to produce up to 2.5-mM 2,3-BDO from crystalline cellulose and xylan and 0.2-mM 2,3-BDO directly from unpretreated switchgrass. This serves as the basis for higher yields and productivities, and to this end, limiting factors and potential genetic targets for further optimization were assessed using the genome-scale metabolic model of C. bescii.IMPORTANCELignocellulosic plant biomass as the substrate for microbial synthesis of 2,3-butanediol is one of the major keys toward cost-effective bio-based production of this chemical at an industrial scale. However, deconstruction of biomass to release the sugars for microbial growth currently requires expensive thermochemical and enzymatic pretreatments. In this study, the thermo-cellulolytic bacterium Caldicellulosiruptor bescii was successfully engineered to produce 2,3-butanediol from cellulose, xylan, and directly from unpretreated switchgrass. Genome-scale metabolic modeling of C. bescii was applied to adjust carbon and redox fluxes to maximize productivity of 2,3-butanediol, thereby revealing bottlenecks that require genetic modifications.
Collapse
Affiliation(s)
- Tania N. N. Tanwee
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Gina L. Lipscomb
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Jason L. Vailionis
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, Rhode Island, USA
| | - Ke Zhang
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, Rhode Island, USA
| | - Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Hailey C. O'Quinn
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Farris L. Poole
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Ying Zhang
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, Rhode Island, USA
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| |
Collapse
|
3
|
Bing RG, Willard DJ, Crosby JR, Adams MWW, Kelly RM. Whither the genus Caldicellulosiruptor and the order Thermoanaerobacterales: phylogeny, taxonomy, ecology, and phenotype. Front Microbiol 2023; 14:1212538. [PMID: 37601363 PMCID: PMC10434631 DOI: 10.3389/fmicb.2023.1212538] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/20/2023] [Indexed: 08/22/2023] Open
Abstract
The order Thermoanaerobacterales currently consists of fermentative anaerobic bacteria, including the genus Caldicellulosiruptor. Caldicellulosiruptor are represented by thirteen species; all, but one, have closed genome sequences. Interest in these extreme thermophiles has been motivated not only by their high optimal growth temperatures (≥70°C), but also by their ability to hydrolyze polysaccharides including, for some species, both xylan and microcrystalline cellulose. Caldicellulosiruptor species have been isolated from geographically diverse thermal terrestrial environments located in New Zealand, China, Russia, Iceland and North America. Evidence of their presence in other terrestrial locations is apparent from metagenomic signatures, including volcanic ash in permafrost. Here, phylogeny and taxonomy of the genus Caldicellulosiruptor was re-examined in light of new genome sequences. Based on genome analysis of 15 strains, a new order, Caldicellulosiruptorales, is proposed containing the family Caldicellulosiruptoraceae, consisting of two genera, Caldicellulosiruptor and Anaerocellum. Furthermore, the order Thermoanaerobacterales also was re-assessed, using 91 genome-sequenced strains, and should now include the family Thermoanaerobacteraceae containing the genera Thermoanaerobacter, Thermoanaerobacterium, Caldanaerobacter, the family Caldanaerobiaceae containing the genus Caldanaerobius, and the family Calorimonaceae containing the genus Calorimonas. A main outcome of ANI/AAI analysis indicates the need to reclassify several previously designated species in the Thermoanaerobacterales and Caldicellulosiruptorales by condensing them into strains of single species. Comparative genomics of carbohydrate-active enzyme inventories suggested differentiating phenotypic features, even among strains of the same species, reflecting available nutrients and ecological roles in their native biotopes.
Collapse
Affiliation(s)
- Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| | - Daniel J. Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| | - James R. Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| |
Collapse
|
4
|
Bing RG, Carey MJ, Laemthong T, Willard DJ, Crosby JR, Sulis DB, Wang JP, Adams MWW, Kelly RM. Fermentative conversion of unpretreated plant biomass: A thermophilic threshold for indigenous microbial growth. BIORESOURCE TECHNOLOGY 2023; 367:128275. [PMID: 36347479 PMCID: PMC10561188 DOI: 10.1016/j.biortech.2022.128275] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/31/2022] [Accepted: 11/01/2022] [Indexed: 06/16/2023]
Abstract
Naturally occurring, microbial contaminants were found in plant biomasses from common bioenergy crops and agricultural wastes. Unexpectedly, indigenous thermophilic microbes were abundant, raising the question of whether they impact thermophilic consolidated bioprocessing fermentations that convert biomass directly into useful bioproducts. Candidate microbial platforms for biomass conversion, Acetivibrio thermocellus (basionym Clostridium thermocellum; Topt 60 °C) and Caldicellulosiruptor bescii (Topt 78 °C), each degraded a wide variety of plant biomasses, but only A. thermocellus was significantly affected by the presence of indigenous microbial populations harbored by the biomass. Indigenous microbial growth was eliminated at ≥75 °C, conditions where C. bescii thrives, but where A. thermocellus cannot survive. Therefore, 75 °C is the thermophilic threshold to avoid sterilizing pre-treatments on the biomass that prevents native microbes from competing with engineered microbes and forming undesirable by-products. Thermophiles that naturally grow at and above 75 °C offer specific advantages as platform microorganisms for biomass conversion into fuels and chemicals.
Collapse
Affiliation(s)
- Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Morgan J Carey
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Tunyaboon Laemthong
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Daniel J Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - James R Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Daniel B Sulis
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, United States
| | - Jack P Wang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, United States
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, United States
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States.
| |
Collapse
|
5
|
Swinnen S, Zurek C, Krämer M, Heger RM, Domeyer JE, Ziegler J, Svetlitchnyi VA, Läufer A. A novel SfaNI-like restriction-modification system in Caldicellulosiruptor extents the genetic engineering toolbox for this genus. PLoS One 2022; 17:e0279562. [PMID: 36580476 PMCID: PMC9799307 DOI: 10.1371/journal.pone.0279562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 12/11/2022] [Indexed: 12/30/2022] Open
Abstract
Caldicellulosiruptor is a genus of thermophilic to hyper-thermophilic microorganisms that express and secrete an arsenal of enzymes degrading lignocellulosic biomasses into fermentable sugars. Because of this distinguished feature, strains of Caldicellulosiruptor have been considered as promising candidates for consolidated bioprocessing. Although a few Caldicellulosiruptor strains with industrially relevant characteristics have been isolated to date, it is apparent that further improvement of the strains is essential for industrial application. The earlier identification of the HaeIII-like restriction-modification system in C. bescii strain DSM 6725 has formed the basis for genetic methods with the aim to improve the strain's lignocellulolytic activity and ethanol production. In this study, a novel SfaNI-like restriction-modification system was identified in Caldicellulosiruptor sp. strain BluCon085, consisting of an endonuclease and two methyltransferases that recognize the reverse-complement sequences 5'-GATGC-3' and 5'-GCATC-3'. Methylation of the adenine in both sequences leads to an asymmetric methylation pattern in the genomic DNA of strain BluCon085. Proteins with high percentage of identity to the endonuclease and two methyltransferases were identified in the genomes of C. saccharolyticus strain DSM 8903, C. naganoensis strain DSM 8991, C. changbaiensis strain DSM 26941 and Caldicellulosiruptor sp. strain F32, suggesting that a similar restriction-modification system may be active also in these strains and respective species. We show that methylation of plasmid and linear DNA by the identified methyltransferases, obtained by heterologous expression in Escherichia coli, is sufficient for successful transformation of Caldicellulosiruptor sp. strain DIB 104C. The genetic engineering toolbox developed in this study forms the basis for rational strain improvement of strain BluCon085, a derivative from strain DIB 104C with exceptionally high L-lactic acid production. The toolbox may also work for other species of the genus Caldicellulosiruptor that have so far not been genetically tractable.
Collapse
|
6
|
Laemthong T, Bing RG, Crosby JR, Adams MWW, Kelly RM. Engineering Caldicellulosiruptor bescii with Surface Layer Homology Domain-Linked Glycoside Hydrolases Improves Plant Biomass Solubilization. Appl Environ Microbiol 2022; 88:e0127422. [PMID: 36169328 PMCID: PMC9599439 DOI: 10.1128/aem.01274-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 09/12/2022] [Indexed: 11/20/2022] Open
Abstract
Extremely thermophilic Caldicellulosiruptor species solubilize carbohydrates from lignocellulose through glycoside hydrolases (GHs) that can be extracellular, intracellular, or cell surface layer (S-layer) associated. Caldicellulosiruptor genomes sequenced so far encode at least one surface layer homology domain glycoside hydrolase (SLH-GH), representing six different classes of these enzymes; these can have multiple binding and catalytic domains. Biochemical characterization of a representative from each class was done to determine their biocatalytic features: four SLH-GHs from Caldicellulosiruptor kronotskyensis (Calkro_0111, Calkro_0402, Calkro_0072, and Calkro_2036) and two from Caldicellulosiruptor hydrothermalis (Calhy_1629 and Calhy_2383). Calkro_0111, Calkro_0072, and Calhy_2383 exhibited β-1,3-glucanase activity, Calkro_0402 was active on both β-1,3/1,4-glucan and β-1,4-xylan, Calkro_2036 exhibited activity on both β-1,3/1,4-glucan and β-1,4-glucan, and Calhy_1629 was active only on arabinan. Caldicellulosiruptor bescii, the only species with molecular genetic tools as well as already a strong cellulose degrader, contains only one SLH-GH, Athe_0594, a glucanase that is a homolog of Calkro_2036; the other 5 classes of SLH-GHs are absent in C. bescii. The C. bescii secretome, supplemented with individual enzymes or cocktails of SLH-GHs, increased in vitro sugar release from sugar cane bagasse and poplar. Expression of non-native SLH-GHs in vivo, either associated with the S-layer or as freely secreted enzymes, improved total carbohydrate solubilization of sugar cane bagasse and poplar by up to 45% and 23%, respectively. Most notably, expression of Calkro_0402, a xylanase/glucanase, improved xylose solubilization from poplar and bagasse by over 70% by C. bescii. While Caldicellulosiruptor species are already prolific lignocellulose degraders, they can be further improved by the strategy described here. IMPORTANCE Caldicellulosiruptor species hold promise as microorganisms that can solubilize the carbohydrate portion of lignocellulose and subsequently convert fermentable sugars into bio-based chemicals and fuels. Members of the genus have surface layer (S-layer) homology domain-associated glycoside hydrolases (SLH-GHs) that mediate attachment to biomass as well as hydrolysis of carbohydrates. Caldicellulosiruptor bescii, the most studied member of the genus, has only one SLH-GH. Expression of SLH-GHs from other Caldicellulosiruptor species in C. bescii significantly improved degradation of sugar cane bagasse and poplar. This suggests that this extremely thermophilic bacterium can be engineered to further improve its ability to degrade specific plant biomasses by inserting genes encoding SLH-GHs recruited from other Caldicellulosiruptor species.
Collapse
Affiliation(s)
- Tunyaboon Laemthong
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - James R. Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| |
Collapse
|
7
|
Bing RG, Straub CT, Sulis DB, Wang JP, Adams MWW, Kelly RM. Plant biomass fermentation by the extreme thermophile Caldicellulosiruptor bescii for co-production of green hydrogen and acetone: Technoeconomic analysis. BIORESOURCE TECHNOLOGY 2022; 348:126780. [PMID: 35093526 PMCID: PMC10560548 DOI: 10.1016/j.biortech.2022.126780] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 01/18/2022] [Accepted: 01/23/2022] [Indexed: 06/14/2023]
Abstract
A variety of chemical and biological processes have been proposed for conversion of sustainable low-cost feedstocks into industrial products. Here, a biorefinery concept is formulated, modeled, and analyzed in which a naturally (hemi)cellulolytic and extremely thermophilic bacterium, Caldicellulosiruptor bescii, is metabolically engineered to convert the carbohydrate content of lignocellulosic biomasses (i.e., soybean hulls, transgenic poplar) into green hydrogen and acetone. Experimental validation of C. bescii fermentative performance demonstrated 82% carbohydrate solubilization of soybean hulls and 55% for transgenic poplar. A detailed technical design, including equipment specifications, provides the basis for an economic analysis that establishes metabolic engineering targets. This robust industrial process leveraging metabolically engineered C. bescii yields 206 kg acetone and 25 kg H2 per metric ton of soybean hull, or 174 kg acetone and 21 kg H2 per metric ton transgenic poplar. Beyond this specific case, the model demonstrates industrial feasibility and economic advantages of thermophilic fermentation.
Collapse
Affiliation(s)
- Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Christopher T Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Daniel B Sulis
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, United States
| | - Jack P Wang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, United States
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, United States
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States.
| |
Collapse
|
8
|
Ashokkumar V, Venkatkarthick R, Jayashree S, Chuetor S, Dharmaraj S, Kumar G, Chen WH, Ngamcharussrivichai C. Recent advances in lignocellulosic biomass for biofuels and value-added bioproducts - A critical review. BIORESOURCE TECHNOLOGY 2022; 344:126195. [PMID: 34710596 DOI: 10.1016/j.biortech.2021.126195] [Citation(s) in RCA: 102] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/16/2021] [Accepted: 10/19/2021] [Indexed: 06/13/2023]
Abstract
Lignocellulosic biomass is a highly renewable, economical, and carbon-neutral feedstock containing sugar-rich moieties that can be processed to produce second-generation biofuels and bio-sourced compounds. However, due to their heterogeneous multi-scale structure, the lignocellulosic materials have major limitations to valorization and exhibit recalcitrance to saccharification or hydrolysis by enzymes. In this context, this review focuses on the latest methods available and state-of-the-art technologies in the pretreatment of lignocellulosic biomass, which aids the disintegration of the complex materials into monomeric units. In addition, this review deals with the genetic engineering techniques to develop advanced strategies for fermentation processes or microbial cell factories to generate desired products in native or modified hosts. Further, it also intends to bridge the gap in developing various economically feasible lignocellulosic products and chemicals using biorefining technologies.
Collapse
Affiliation(s)
- Veeramuthu Ashokkumar
- Center of Excellence in Catalysis for Bioenergy and Renewable Chemicals (CBRC), Faculty of Science, Chulalongkorn University, Pathum Wan, Bangkok 10330, Thailand.
| | | | - Shanmugam Jayashree
- Department of Biotechnology, Stella Maris College (Autonomous), Chennai, Tamil Nadu 600086, India
| | - Santi Chuetor
- Department of Chemical Engineering, Faculty of Engineering, King Mongkut's University of Technology North Bangkok (KMUTNB), Bangkok, Thailand
| | - Selvakumar Dharmaraj
- Department of Marine Biotechnology, Academy of Maritime Education and Training [AMET] (Deemed to be University), Chennai 603112, Tamil Nadu, India
| | - Gopalakrishnan Kumar
- School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea; Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Box 8600 Forus, 4036 Stavanger, Norway
| | - Wei-Hsin Chen
- Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan
| | - Chawalit Ngamcharussrivichai
- Center of Excellence in Catalysis for Bioenergy and Renewable Chemicals (CBRC), Faculty of Science, Chulalongkorn University, Pathum Wan, Bangkok 10330, Thailand; Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand
| |
Collapse
|
9
|
Zhang K, Zhao W, Rodionov DA, Rubinstein GM, Nguyen DN, Tanwee TNN, Crosby J, Bing RG, Kelly RM, Adams MWW, Zhang Y. Genome-Scale Metabolic Model of Caldicellulosiruptor bescii Reveals Optimal Metabolic Engineering Strategies for Bio-based Chemical Production. mSystems 2021; 6:e0135120. [PMID: 34060912 PMCID: PMC8269263 DOI: 10.1128/msystems.01351-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 05/04/2021] [Indexed: 12/03/2022] Open
Abstract
Metabolic modeling was used to examine potential bottlenecks that could be encountered for metabolic engineering of the cellulolytic extreme thermophile Caldicellulosiruptor bescii to produce bio-based chemicals from plant biomass. The model utilizes subsystems-based genome annotation, targeted reconstruction of carbohydrate utilization pathways, and biochemical and physiological experimental validations. Specifically, carbohydrate transport and utilization pathways involving 160 genes and their corresponding functions were incorporated, representing the utilization of C5/C6 monosaccharides, disaccharides, and polysaccharides such as cellulose and xylan. To illustrate its utility, the model predicted that optimal production from biomass-based sugars of the model product, ethanol, was driven by ATP production, redox balancing, and proton translocation, mediated through the interplay of an ATP synthase, a membrane-bound hydrogenase, a bifurcating hydrogenase, and a bifurcating NAD- and NADP-dependent oxidoreductase. These mechanistic insights guided the design and optimization of new engineering strategies for product optimization, which were subsequently tested in the C. bescii model, showing a nearly 2-fold increase in ethanol yields. The C. bescii model provides a useful platform for investigating the potential redox controls that mediate the carbon and energy flows in metabolism and sets the stage for future design of engineering strategies aiming at optimizing the production of ethanol and other bio-based chemicals. IMPORTANCE The extremely thermophilic cellulolytic bacterium, Caldicellulosiruptor bescii, degrades plant biomass at high temperatures without any pretreatments and can serve as a strategic platform for industrial applications. The metabolic engineering of C. bescii, however, faces potential bottlenecks in bio-based chemical productions. By simulating the optimal ethanol production, a complex interplay between redox balancing and the carbon and energy flow was revealed using a C. bescii genome-scale metabolic model. New engineering strategies were designed based on an improved mechanistic understanding of the C. bescii metabolism, and the new designs were modeled under different genetic backgrounds to identify optimal strategies. The C. bescii model provided useful insights into the metabolic controls of this organism thereby opening up prospects for optimizing production of a wide range of bio-based chemicals.
Collapse
Affiliation(s)
- Ke Zhang
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, Rhode Island, USA
| | - Weishu Zhao
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, Rhode Island, USA
| | - Dmitry A. Rodionov
- Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, USA
- A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
| | - Gabriel M. Rubinstein
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Diep N. Nguyen
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Tania N. N. Tanwee
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - James Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Ying Zhang
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, Rhode Island, USA
| |
Collapse
|
10
|
Krska D, Mazurkewich S, Brown HA, Theibich Y, Poulsen JCN, Morris AL, Koropatkin NM, Lo Leggio L, Larsbrink J. Structural and Functional Analysis of a Multimodular Hyperthermostable Xylanase-Glucuronoyl Esterase from Caldicellulosiruptor kristjansonii. Biochemistry 2021; 60:2206-2220. [PMID: 34180241 PMCID: PMC8280721 DOI: 10.1021/acs.biochem.1c00305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The hyperthermophilic bacterium Caldicellulosiruptor kristjansonii encodes an unusual enzyme, CkXyn10C-GE15A, which
incorporates two catalytic domains, a xylanase and a glucuronoyl esterase,
and five carbohydrate-binding modules (CBMs) from families 9 and 22.
The xylanase and glucuronoyl esterase catalytic domains were recently
biochemically characterized, as was the ability of the individual
CBMs to bind insoluble polysaccharides. Here, we further probed the
abilities of the different CBMs from CkXyn10C-GE15A
to bind to soluble poly- and oligosaccharides using affinity gel electrophoresis,
isothermal titration calorimetry, and differential scanning fluorimetry.
The results revealed additional binding properties of the proteins
compared to the former studies on insoluble polysaccharides. Collectively,
the results show that all five CBMs have their own distinct binding
preferences and appear to complement each other and the catalytic
domains in targeting complex cell wall polysaccharides. Additionally,
through renewed efforts, we have achieved partial structural characterization
of this complex multidomain protein. We have determined the structures
of the third CBM9 domain (CBM9.3) and the glucuronoyl esterase (GE15A)
by X-ray crystallography. CBM9.3 is the second CBM9 structure determined
to date and was shown to bind oligosaccharide ligands at the same
site but in a different binding mode compared to that of the previously
determined CBM9 structure from Thermotoga maritima. GE15A represents a unique intermediate between reported fungal
and bacterial glucuronoyl esterase structures as it lacks two inserted
loop regions typical of bacterial enzymes and a third loop has an
atypical structure. We also report small-angle X-ray scattering measurements
of the N-terminal CBM22.1–CBM22.2–Xyn10C construct,
indicating a compact arrangement at room temperature.
Collapse
Affiliation(s)
- Daniel Krska
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Scott Mazurkewich
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.,Wallenberg Wood Science Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Haley A Brown
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States
| | - Yusuf Theibich
- Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | | | - Adeline L Morris
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States
| | - Nicole M Koropatkin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Johan Larsbrink
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.,Wallenberg Wood Science Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| |
Collapse
|
11
|
Bing RG, Sulis DB, Wang JP, Adams MW, Kelly RM. Thermophilic microbial deconstruction and conversion of natural and transgenic lignocellulose. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:272-293. [PMID: 33684253 PMCID: PMC10519370 DOI: 10.1111/1758-2229.12943] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/25/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
The potential to convert renewable plant biomasses into fuels and chemicals by microbial processes presents an attractive, less environmentally intense alternative to conventional routes based on fossil fuels. This would best be done with microbes that natively deconstruct lignocellulose and concomitantly form industrially relevant products, but these two physiological and metabolic features are rarely and simultaneously observed in nature. Genetic modification of both plant feedstocks and microbes can be used to increase lignocellulose deconstruction capability and generate industrially relevant products. Separate efforts on plants and microbes are ongoing, but these studies lack a focus on optimal, complementary combinations of these disparate biological systems to obtain a convergent technology. Improving genetic tools for plants have given rise to the generation of low-lignin lines that are more readily solubilized by microorganisms. Most focus on the microbiological front has involved thermophilic bacteria from the genera Caldicellulosiruptor and Clostridium, given their capacity to degrade lignocellulose and to form bio-products through metabolic engineering strategies enabled by ever-improving molecular genetics tools. Bioengineering plant properties to better fit the deconstruction capabilities of candidate consolidated bioprocessing microorganisms has potential to achieve the efficient lignocellulose deconstruction needed for industrial relevance.
Collapse
Affiliation(s)
- Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Daniel B. Sulis
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695
| | - Jack P. Wang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695
| | - Michael W.W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| |
Collapse
|
12
|
Kato J, Takemura K, Kato S, Fujii T, Wada K, Iwasaki Y, Aoi Y, Matsushika A, Murakami K, Nakashimada Y. Metabolic engineering of Moorella thermoacetica for thermophilic bioconversion of gaseous substrates to a volatile chemical. AMB Express 2021; 11:59. [PMID: 33891189 PMCID: PMC8065083 DOI: 10.1186/s13568-021-01220-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Accepted: 04/09/2021] [Indexed: 11/26/2022] Open
Abstract
Gas fermentation is one of the promising bioprocesses to convert CO2 or syngas to important chemicals. Thermophilic gas fermentation of volatile chemicals has the potential for the development of consolidated bioprocesses that can simultaneously separate products during fermentation. This study reports the production of acetone from CO2 and H2, CO, or syngas by introducing the acetone production pathway using acetyl–coenzyme A (Ac-CoA) and acetate produced via the Wood–Ljungdahl pathway in Moorella thermoacetica. Reducing the carbon flux from Ac-CoA to acetate through genetic engineering successfully enhanced acetone productivity, which varied on the basis of the gas composition. The highest acetone productivity was obtained with CO–H2, while autotrophic growth collapsed with CO2–H2. By adding H2 to CO, the acetone productivity from the same amount of carbon source increased compared to CO gas only, and the maximum specific acetone production rate also increased from 0.04 to 0.09 g-acetone/g-dry cell/h. Our development of the engineered thermophilic acetogen M. thermoacetica, which grows at a temperature higher than the boiling point of acetone (58 °C), would pave the way for developing a consolidated process with simplified and cost-effective recovery via condensation following gas fermentation.
Collapse
|