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Senanayake M, Lin CY, Mansfield SD, Eudes A, Davison BH, Pingali SV, O'Neill H. Ectopic Production of 3,4-Dihydroxybenzoate in Planta Affects Cellulose Structure and Organization. Biomacromolecules 2024; 25:3542-3553. [PMID: 38780531 DOI: 10.1021/acs.biomac.4c00187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Lignocellulosic biomass is a highly sustainable and largely carbon dioxide neutral feedstock for the production of biofuels and advanced biomaterials. Although thermochemical pretreatment is typically used to increase the efficiency of cell wall deconstruction, genetic engineering of the major plant cell wall polymers, especially lignin, has shown promise as an alternative approach to reduce biomass recalcitrance. Poplar trees with reduced lignin content and altered composition were previously developed by overexpressing bacterial 3-dehydroshikimate dehydratase (QsuB) enzyme to divert carbon flux from the shikimate pathway. In this work, three transgenic poplar lines with increasing QsuB expression levels and different lignin contents were studied using small-angle neutron scattering (SANS) and wide-angle X-ray scattering (WAXS). SANS showed that although the cellulose microfibril cross-sectional dimension remained unchanged, the ordered organization of the microfibrils progressively decreased with increased QsuB expression. This was correlated with decreasing total lignin content in the QsuB lines. WAXS showed that the crystallite dimensions of cellulose microfibrils transverse to the growth direction were not affected by the QsuB expression, but the crystallite dimensions parallel to the growth direction were decreased by ∼20%. Cellulose crystallinity was also decreased with increased QsuB expression, which could be related to high levels of 3,4-dihydroxybenzoate, the product of QsuB expression, disrupting microfibril crystallization. In addition, the cellulose microfibril orientation angle showed a bimodal distribution at higher QsuB expression levels. Overall, this study provides new structural insights into the impact of ectopic synthesis of small-molecule metabolites on cellulose organization and structure that can be used for future efforts aimed at reducing biomass recalcitrance.
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Affiliation(s)
- Manjula Senanayake
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Chien-Yuan Lin
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Shawn D Mansfield
- Department of Wood Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Aymerick Eudes
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Brian H Davison
- BioSciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Sai Venkatesh Pingali
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Hugh O'Neill
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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2
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Xiao X, Hu H, Meng X, Huang Z, Feng Y, Gao Q, Ruan W. Volatile fatty acids production from kitchen waste slurry using anaerobic membrane bioreactor via alkaline fermentation with high salinity: Evaluation on process performance and microbial succession. BIORESOURCE TECHNOLOGY 2024; 399:130576. [PMID: 38479625 DOI: 10.1016/j.biortech.2024.130576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 03/08/2024] [Accepted: 03/10/2024] [Indexed: 03/22/2024]
Abstract
In this study, a pilot-scale anaerobic membrane bioreactor (AnMBR) was developed to continuously produce volatile fatty acids (VFAs) from kitchen waste slurry under an alkaline condition. The alkaline fermentation effectively suppressed methanogenesis, thus achieving high VFAs production of 60.3 g/L. Acetic acid, propionic acid, and butyric acid accounted for over 95.0 % of the total VFAs. The VFAs yield, productivity, and chemical oxygen demand (COD) recovery efficiency reached 0.5 g/g-CODinfluent, 6.0 kg/m3/d, and 62.8 %, respectively. Moreover, the CODVFAs/CODeffluent ratio exceeded 96.0 %, and the CODVFAs/NH3-N ratio through ammonia distillation reached up to 192.5. The microbial community was reshaped during the alkaline fermentation with increasing salinity. The membrane fouling of the AnMBR was alleviated by chemical cleaning and sludge discharge, and membrane modules displayed a sustained filtration performance. In conclusion, this study demonstrated that high-quality VFAs could be efficiently produced from kitchen waste slurry using an AnMBR process via alkaline fermentation.
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Affiliation(s)
- Xiaolan Xiao
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China; Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou University of Science and Technology, Suzhou 215009, PR China
| | - Hongmei Hu
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China
| | - Xingyao Meng
- Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry, Beijing Technology and Business University, Beijing 100048, PR China
| | - Zhenxing Huang
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China; Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry, Beijing Technology and Business University, Beijing 100048, PR China.
| | - Yongrui Feng
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China
| | - Qi Gao
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China
| | - Wenquan Ruan
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, PR China; Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou University of Science and Technology, Suzhou 215009, PR China
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3
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Hunter C, Sun Z, Mansfield SD, Shahbaz M, Pilon M, Gleason SM. The effects of copper deficiency on lignification, xylem vessel structure, and hydraulic traits in hybrid poplar. PHYSIOLOGIA PLANTARUM 2023; 175:e14006. [PMID: 37882274 DOI: 10.1111/ppl.14006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 06/19/2023] [Accepted: 08/14/2023] [Indexed: 10/27/2023]
Abstract
Copper (Cu) homeostasis is integral to many plant physiological processes, including lignification of plant cell walls. This link occurs through Cu's role as a cofactor in the apoplastic laccase enzymes that oxidize monolignols that then polymerize to form the hydrophobic lignin polymer, which provides rigidity and strength to the water transport system. In this study, we investigated the effect of Cu deficiency on lignin content and chemistry in poplar stems. We also examined the effect of Cu deficiency on the stiffness of stem wood and the hydraulic properties of leaves. Cu deficiency resulted in a significant reduction in lignin content, an increase in the syringyl to guaiacyl monomer ratio of stem xylem, and no change to stem modulus of elasticity. Accompanying these stem traits, Cu-deficient leaves had higher (less negative) turgor loss points and markedly stiffer mesophyll cell walls. Our results may reflect a novel response in poplar whereby structural stiffness and mechanical stability are maintained in the face of Cu deficiency and reduction in the guaiacyl lignin monomer content.
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Affiliation(s)
- Cameron Hunter
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Water Management and Systems Research Unit, USDA-ARS, Fort Collins, Colorado, USA
| | - Zimou Sun
- Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shawn D Mansfield
- Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada
- Botany Department, University of British Columbia, Vancouver, British Columbia, Canada
| | - Muhammad Shahbaz
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Marinus Pilon
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Sean M Gleason
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Water Management and Systems Research Unit, USDA-ARS, Fort Collins, Colorado, USA
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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.
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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.
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Biswal AK, Hengge NN, Black IM, Atmodjo MA, Mohanty SS, Ryno D, Himmel ME, Azadi P, Bomble YJ, Mohnen D. Composition and yield of non-cellulosic and cellulosic sugars in soluble and particulate fractions during consolidated bioprocessing of poplar biomass by Clostridium thermocellum. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:23. [PMID: 35227303 PMCID: PMC8887089 DOI: 10.1186/s13068-022-02119-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Terrestrial plant biomass is the primary renewable carbon feedstock for enabling transition to a sustainable bioeconomy. Consolidated bioprocessing (CBP) by the cellulolytic thermophile Clostridium thermocellum offers a single step microbial platform for production of biofuels and biochemicals via simultaneous solubilization of carbohydrates from lignocellulosic biomass and conversion to products. Here, solubilization of cell wall cellulosic, hemicellulosic, and pectic polysaccharides in the liquor and solid residues generated during CBP of poplar biomass by C. thermocellum was analyzed. RESULTS The total amount of biomass solubilized in the C. thermocellum DSM1313 fermentation platform was 5.8, 10.3, and 13.7% of milled non-pretreated poplar after 24, 48, and 120 h, respectively. These results demonstrate solubilization of 24% cellulose and 17% non-cellulosic sugars after 120 h, consistent with prior reports. The net solubilization of non-cellulosic sugars by C. thermocellum (after correcting for the uninoculated control fermentations) was 13 to 36% of arabinose (Ara), xylose (Xyl), galactose (Gal), mannose (Man), and glucose (Glc); and 15% and 3% of fucose and glucuronic acid, respectively. No rhamnose was solubilized and 71% of the galacturonic acid (GalA) was solubilized. These results indicate that C. thermocellum may be selective for the types and/or rate of solubilization of the non-cellulosic wall polymers. Xyl, Man, and Glc were found to accumulate in the fermentation liquor at levels greater than in uninoculated control fermentations, whereas Ara and Gal did not accumulate, suggesting that C. thermocellum solubilizes both hemicelluloses and pectins but utilizes them differently. After five days of fermentation, the relative amount of Rha in the solid residues increased 21% indicating that the Rha-containing polymer rhamnogalacturonan I (RG-I) was not effectively solubilized by C. thermocellum CBP, a result confirmed by immunoassays. Comparison of the sugars in the liquor versus solid residue showed that C. thermocellum solubilized hemicellulosic xylan and mannan, but did not fully utilize them, solubilized and appeared to utilize pectic homogalacturonan, and did not solubilize RG-I. CONCLUSIONS The significant relative increase in RG-I in poplar solid residues following CBP indicates that C. thermocellum did not solubilize RG-I. These results support the hypothesis that this pectic glycan may be one barrier for efficient solubilization of poplar by C. thermocellum.
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Affiliation(s)
- Ajaya K. Biswal
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Neal N. Hengge
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA
| | - Ian M. Black
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Melani A. Atmodjo
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Sushree S. Mohanty
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - David Ryno
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Michael E. Himmel
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Yannick J. Bomble
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA
| | - Debra Mohnen
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
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Du T, Feng L, Zhen X. Microbial community structures and antibiotic biodegradation characteristics during anaerobic digestion of chicken manure containing residual enrofloxacin. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2022; 57:102-113. [PMID: 35037829 DOI: 10.1080/03601234.2022.2026124] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
To explore the interaction between the residual antibiotic in animal manure and biological treatment, the effect of enrofloxacin (ENR) on the anaerobic digestion of chicken manure, and biodegradation rate of ENR was studied under the condition of actual residual ENR content of 0, 8, 16 and 32 mg/kg·TS. The results showed that the addition of ENR increased the total biogas production, especially 8 mg/kg·TS promoted the anaerobic reaction obviously, and the corresponding cumulative biogas production was increased by 15.33%. However, in the presence of 32 mg/kg·TS, the biogas production rate was reduced and the peak period of biogas production was delayed. The results of enzyme activities determination and 16S rRNA sequencing showed that ENR had different effects on archaea and bacteria. The residual ENR could promote hydrolysis reactions in the anaerobic system, but could inhibit acetoclastic methanogens, and the relative abundance of Methanosaeta declined by 7.22‒12.41%. The first-order kinetic model showed that the half-life period of ENR in the anaerobic digestion system was 9.16‒10.83 days, and the biodegradation rate exceeded 80% after the treatment. This study can bring important information for the management of animal manure in the future.
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Affiliation(s)
- Tie Du
- College of Energy and Environment, Shenyang Aerospace University, Shenyang, China
| | - Lei Feng
- College of Energy and Environment, Shenyang Aerospace University, Shenyang, China
| | - Xiaofei Zhen
- School of New Energy and Power Engineering, Lanzhou Jiaotong University, Lanzhou, China
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7
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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.
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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
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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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Straub CT, Bing RG, Wang JP, Chiang VL, Adams MWW, Kelly RM. Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:43. [PMID: 32180826 PMCID: PMC7065347 DOI: 10.1186/s13068-020-01675-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 02/04/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND Biological conversion of lignocellulosic biomass is significantly hindered by feedstock recalcitrance, which is typically assessed through an enzymatic digestion assay, often preceded by a thermal and/or chemical pretreatment. Here, we assay 17 lines of unpretreated transgenic black cottonwood (Populus trichocarpa) utilizing a lignocellulose-degrading, metabolically engineered bacterium, Caldicellulosiruptor bescii. The poplar lines were assessed by incubation with an engineered C. bescii strain that solubilized and converted the hexose and pentose carbohydrates to ethanol and acetate. The resulting fermentation titer and biomass solubilization were then utilized as a measure of biomass recalcitrance and compared to data previously reported on the transgenic poplar samples. RESULTS Of the 17 transgenic poplar lines examined with C. bescii, a wide variation in solubilization and fermentation titer was observed. While the wild type poplar control demonstrated relatively high recalcitrance with a total solubilization of only 20% and a fermentation titer of 7.3 mM, the transgenic lines resulted in solubilization ranging from 15 to 79% and fermentation titers from 6.8 to 29.6 mM. Additionally, a strong inverse correlation (R 2 = 0.8) between conversion efficiency and lignin content was observed with lower lignin samples more easily converted and solubilized by C. bescii. CONCLUSIONS Feedstock recalcitrance can be significantly reduced with transgenic plants, but finding the correct modification may require a large sample set to identify the most advantageous genetic modifications for the feedstock. Utilizing C. bescii as a screening assay for recalcitrance, poplar lines with down-regulation of coumarate 3-hydroxylase 3 (C3H3) resulted in the highest degrees of solubilization and conversion by C. bescii. One such line, with a growth phenotype similar to the wild-type, generated more than three times the fermentation products of the wild-type poplar control, suggesting that excellent digestibility can be achieved without compromising fitness of the tree.
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Affiliation(s)
- Christopher T. Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, EB-1, 911 Partners Way, Raleigh, NC 27695-7905 USA
| | - Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, EB-1, 911 Partners Way, Raleigh, NC 27695-7905 USA
| | - Jack P. Wang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695 USA
| | - Vincent L. Chiang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695 USA
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, EB-1, 911 Partners Way, Raleigh, NC 27695-7905 USA
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Prasad RK, Chatterjee S, Mazumder PB, Gupta SK, Sharma S, Vairale MG, Datta S, Dwivedi SK, Gupta DK. Bioethanol production from waste lignocelluloses: A review on microbial degradation potential. CHEMOSPHERE 2019; 231:588-606. [PMID: 31154237 DOI: 10.1016/j.chemosphere.2019.05.142] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 04/02/2019] [Accepted: 05/17/2019] [Indexed: 05/15/2023]
Abstract
Tremendous explosion of population has led to about 200% increment of total energy consumptions in last twenty-five years. Apart from conventional fossil fuel as limited energy source, alternative non-conventional sources are being explored worldwide to cater the energy requirement. Lignocellulosic biomass conversion for biofuel production is an important alternative energy source due to its abundance in nature and creating less harmful impacts on the environment in comparison to the coal or petroleum-based sources. However, lignocellulose biopolymer, the building block of plants, is a recalcitrant substance and difficult to break into desirable products. Commonly used chemical and physical methods for pretreating the substrate are having several limitations. Whereas, utilizing microbial potential to hydrolyse the biomass is an interesting area of research. Because of the complexity of substrate, several enzymes are required that can act synergistically to hydrolyse the biopolymer producing components like bioethanol or other energy substances. Exploring a range of microorganisms, like bacteria, fungi, yeast etc. that utilizes lignocelluloses for their energy through enzymatic breaking down the biomass, is one of the options. Scientists are working upon designing organisms through genetic engineering tools to integrate desired enzymes into a single organism (like bacterial cell). Studies on designer cellulosomes and bacteria consortia development relating consolidated bioprocessing are exciting to overcome the issue of appropriate lignocellulose digestions. This review encompasses up to date information on recent developments for effective microbial degradation processes of lignocelluloses for improved utilization to produce biofuel (bioethanol in particular) from the most plentiful substances of our planet.
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Affiliation(s)
- Rajesh Kumar Prasad
- Defence Research Laboratory, DRDO, Tezpur, 784001, Assam, India; Assam University, Silchar, 788011, Assam, India
| | | | | | | | - Sonika Sharma
- Defence Research Laboratory, DRDO, Tezpur, 784001, Assam, India
| | | | | | | | - Dharmendra Kumar Gupta
- Gottfried Wilhelm Leibniz Universität Hannover, Institut für Radioökologie und Strahlenschutz (IRS), HerrenhäuserStr. 2, 30419, Hannover, Germany
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Froese A, Schellenberg J, Sparling R. Enhanced depolymerization and utilization of raw lignocellulosic material by co-cultures of Ruminiclostridium thermocellum with hemicellulose-utilizing partners. Can J Microbiol 2019; 65:296-307. [PMID: 30608879 DOI: 10.1139/cjm-2018-0535] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ruminiclostridium thermocellum is one of the most promising candidates for consolidated bioprocessing (CBP) of low-cost lignocellulosic materials to biofuels but it still shows poor performance in its ability to deconstruct untreated lignocellulosic substrates. One promising approach to increase R. thermocellum's rate of hydrolysis is to co-culture this cellulose-specialist with partners that possess synergistic hydrolysis enzymes and metabolic capabilities. We have created co-cultures of R. thermocellum with two hemicellulose utilizers, Ruminiclostridium stercorarium and Thermoanaerobacter thermohydrosulfuricus, both of which secrete xylanolytic enzymes and utilize the pentose oligo- and monosaccharides that inhibit R. thermocellum's hydrolysis and metabolism. When grown on milled wheat straw, the co-cultures were able to solubilize up to 58% more of the total polysaccharides than the R. thermocellum mono-culture control. Repeated passaging of the co-cultures on wheat straw yielded stable populations with reduced R. thermocellum cell numbers, indicating competition for cellodextrins released from cellulose hydrolysis, although these stabilized co-cultures were still able to outperform the mono-culture controls. Repeated passaging on Avicel cellulose also yielded stable populations. Overall, the observed synergism suggests that co-culturing R. thermocellum with other members is a viable option for increasing the rate and extent of untreated lignocellulose deconstruction by R. thermocellum for CBP purposes.
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Affiliation(s)
- Alan Froese
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.,Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - John Schellenberg
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.,Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Richard Sparling
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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12
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Kong X, Du J, Ye X, Xi Y, Jin H, Zhang M, Guo D. Enhanced methane production from wheat straw with the assistance of lignocellulolytic microbial consortium TC-5. BIORESOURCE TECHNOLOGY 2018; 263:33-39. [PMID: 29729539 DOI: 10.1016/j.biortech.2018.04.079] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/16/2018] [Accepted: 04/20/2018] [Indexed: 06/08/2023]
Abstract
The major obstacle of methane production from lignocellulose lies in the inefficient deconstruction of biomass. In this study, an anaerobic microbial consortium TC-5 was enriched with high lignocellulose-degradation capacity to enhance methane production from wheat straw. High degradation ratio of 45.7% of un-pretreated wheat straw was achieved due to a multi-species lignocellulolytic enzyme presented in the crude culture supernatant. The specific activity of xylanase, xylan esterase and β-xylosidase reached the highest level of 4.23, 0.15 and 0.48 U/mg, while cellobiohydrolase, endoglucanase and β-glucosidase showed the highest specific activity of 0.36, 0.22 and 0.41 U/mg during 9 days' degradation. Inoculation of TC-5 in digestion sludge during anaerobic digestion of wheat straw resulted in remarkable enhancement of 22.2% and 36.6% in methane yield under mesophilic and thermophilic conditions, respectively. This work demonstrates the potential of TC-5 for enhancing the production of biogas and other chemicals through biomass based biorefinery.
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Affiliation(s)
- Xiangping Kong
- East China Scientific Observing and Experimental Station of Development and Utilization of Rural Renewable Energy, Ministry of Agriculture, Biomass Conversion Laboratory, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Science, Nanjing 210014, People's Republic of China
| | - Jing Du
- East China Scientific Observing and Experimental Station of Development and Utilization of Rural Renewable Energy, Ministry of Agriculture, Biomass Conversion Laboratory, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Science, Nanjing 210014, People's Republic of China
| | - Xiaomei Ye
- East China Scientific Observing and Experimental Station of Development and Utilization of Rural Renewable Energy, Ministry of Agriculture, Biomass Conversion Laboratory, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Science, Nanjing 210014, People's Republic of China.
| | - Yonglan Xi
- East China Scientific Observing and Experimental Station of Development and Utilization of Rural Renewable Energy, Ministry of Agriculture, Biomass Conversion Laboratory, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Science, Nanjing 210014, People's Republic of China
| | - Hongmei Jin
- East China Scientific Observing and Experimental Station of Development and Utilization of Rural Renewable Energy, Ministry of Agriculture, Biomass Conversion Laboratory, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Science, Nanjing 210014, People's Republic of China
| | - Min Zhang
- East China Scientific Observing and Experimental Station of Development and Utilization of Rural Renewable Energy, Ministry of Agriculture, Biomass Conversion Laboratory, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Science, Nanjing 210014, People's Republic of China
| | - Dong Guo
- College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Puzhu South Road 30#, Nanjing 211816, People's Republic of China
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13
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Liu H, Sun J, Chang JS, Shukla P. Engineering microbes for direct fermentation of cellulose to bioethanol. Crit Rev Biotechnol 2018; 38:1089-1105. [DOI: 10.1080/07388551.2018.1452891] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Hao Liu
- State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China
| | - Jianliang Sun
- State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China
| | - Jo-Shu Chang
- Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan, China
| | - Pratyoosh Shukla
- Enzyme Technology and Protein Bioinformatics Laboratory, Department of Microbiology, Maharshi Dayanand University, Rohtak, India
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14
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Biomass based hydrogen production by dark fermentation — recent trends and opportunities for greener processes. Curr Opin Biotechnol 2018; 50:136-145. [DOI: 10.1016/j.copbio.2017.12.024] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 12/30/2017] [Indexed: 01/01/2023]
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15
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Chen Y, Zhang M, Xie L, Wang Z, Zhou Q. Molecular-Weight-Fractionation Characteristics and Coagulation Behaviors of Biorecalcitrant Dissolved Organic Matter and Colorants in Cassava Distillery Wastewater. Ind Eng Chem Res 2018. [DOI: 10.1021/acs.iecr.8b00287] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yu Chen
- State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, Institute of Biofilm Technology, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
| | - Ming Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, Institute of Biofilm Technology, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Li Xie
- State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, Institute of Biofilm Technology, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
| | - Zhou Wang
- State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, Institute of Biofilm Technology, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
| | - Qi Zhou
- State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, Institute of Biofilm Technology, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
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16
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Lu T, Liu L, Wei M, Liu Y, Qu Z, Yang C, Wei H, Wei Z. The Effect of Poplar PsnGS1.2 Overexpression on Growth, Secondary Cell Wall, and Fiber Characteristics in Tobacco. FRONTIERS IN PLANT SCIENCE 2018; 9:9. [PMID: 29403519 PMCID: PMC5780347 DOI: 10.3389/fpls.2018.00009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 01/03/2018] [Indexed: 05/23/2023]
Abstract
The glutamine synthetase (GS1) is a key enzyme that catalyzes the reaction of glutamate and ammonia to produce glutamine in the nitrogen (N) metabolism. Previous studies on GS1s in several plant species suggest that overexpression of GS1s can enhance N utilization, accelerate plant vegetative growth, and change wood formation. In this study, we isolated a GS1 gene, termed PsnGS1.2, from Populus simonii × Populus nigra. This gene was expressed at a higher level in roots, and relatively lower but detectable levels in xylem, leaves and phloem of P. simonii × P. nigra. The protein encoded by PsnGS1.2 is primarily located in the cytoplasm. Overexpression of PsnGS1.2 in tobacco led to the increased GS1 activity and IAA content, the augmented N assimilation, and the enlarged leaves with altered anatomical structures. These changes presumably promoted photosynthetic, growth, and biomass productivity. It was noteworthy that the secondary cell walls and fiber characteristics changed remarkably in PsnGS1.2 transgenic tobacco. These changes aligned well with the altered expression levels of the genes involved in fiber development, secondary cell wall component biosynthesis, IAA biosynthesis, amino acid transport, and starch breakdown. Taken together, the results from our study suggest that catalytic functions of PsnGS1.2 on N assimilation and metabolism in transgenic tobacco had significant effects on vegetative growth, leaf development, and secondary cell wall formation and properties through acceleration of photosynthesis and IAA biosynthesis, and redirection of carbon flux to synthesis of more cellulose and hemicellulose.
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Affiliation(s)
- Tingting Lu
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
| | - Lulu Liu
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
| | - Minjing Wei
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
| | - Yingying Liu
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
| | - Zianshang Qu
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
| | - Chuanping Yang
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
| | - Hairong Wei
- School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI, United States
| | - Zhigang Wei
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China
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17
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Whitham JM, Moon JW, Rodriguez M, Engle NL, Klingeman DM, Rydzak T, Abel MM, Tschaplinski TJ, Guss AM, Brown SD. Clostridium thermocellum LL1210 pH homeostasis mechanisms informed by transcriptomics and metabolomics. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:98. [PMID: 29632556 PMCID: PMC5887222 DOI: 10.1186/s13068-018-1095-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 03/24/2018] [Indexed: 05/21/2023]
Abstract
BACKGROUND Clostridium (Ruminiclostridium) thermocellum is a model fermentative anaerobic thermophile being studied and engineered for consolidated bioprocessing of lignocellulosic feedstocks into fuels and chemicals. Engineering efforts have resulted in significant improvements in ethanol yields and titers although further advances are required to make the bacterium industry-ready. For instance, fermentations at lower pH could enable co-culturing with microbes that have lower pH optima, augment productivity, and reduce buffering cost. C. thermocellum is typically grown at neutral pH, and little is known about its pH limits or pH homeostasis mechanisms. To better understand C. thermocellum pH homeostasis we grew strain LL1210 (C. thermocellum DSM1313 Δhpt ΔhydG Δldh Δpfl Δpta-ack), currently the highest ethanol producing strain of C. thermocellum, at different pH values in chemostat culture and applied systems biology tools. RESULTS Clostridium thermocellum LL1210 was found to be growth-limited below pH 6.24 at a dilution rate of 0.1 h-1. F1F0-ATPase gene expression was upregulated while many ATP-utilizing enzymes and pathways were downregulated at pH 6.24. These included most flagella biosynthesis genes, genes for chemotaxis, and other motility-related genes (> 50) as well as sulfate transport and reduction, nitrate transport and nitrogen fixation, and fatty acid biosynthesis genes. Clustering and enrichment of differentially expressed genes at pH values 6.48, pH 6.24 and pH 6.12 (washout conditions) compared to pH 6.98 showed inverse differential expression patterns between the F1F0-ATPase and genes for other ATP-utilizing enzymes. At and below pH 6.24, amino acids including glutamate and valine; long-chain fatty acids, their iso-counterparts and glycerol conjugates; glycolysis intermediates 3-phosphoglycerate, glucose 6-phosphate, and glucose accumulated intracellularly. Glutamate was 267 times more abundant in cells at pH 6.24 compared to pH 6.98, and intercellular concentration reached 1.8 μmol/g pellet at pH 5.80 (stopped flow). CONCLUSIONS Clostridium thermocellum LL1210 can grow under slightly acidic conditions, similar to limits reported for other strains. This foundational study provides a detailed characterization of a relatively acid-intolerant bacterium and provides genetic targets for strain improvement. Future studies should examine adding gene functions used by more acid-tolerant bacteria for improved pH homeostasis at acidic pH values.
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Affiliation(s)
- Jason M. Whitham
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Ji-Won Moon
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Miguel Rodriguez
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Nancy L. Engle
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Dawn M. Klingeman
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Thomas Rydzak
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
- Present Address: Department of Biological Science, University of Calgary, Calgary, AB T2N 1N4 Canada
| | - Malaney M. Abel
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Timothy J. Tschaplinski
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Adam M. Guss
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Steven D. Brown
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
- Present Address: LanzaTech, Inc., Skokie, IL USA
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18
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Verbeke TJ, Garcia GM, Elkins JG. The effect of switchgrass loadings on feedstock solubilization and biofuel production by Clostridium thermocellum. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:233. [PMID: 29213307 PMCID: PMC5708108 DOI: 10.1186/s13068-017-0917-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 08/08/2017] [Indexed: 05/25/2023]
Abstract
BACKGROUND Efficient deconstruction and bioconversion of solids at high mass loadings is necessary to produce industrially relevant titers of biofuels from lignocellulosic biomass. To date, only a few studies have investigated the effect of solids loadings on microorganisms of interest for consolidated bioprocessing. Here, the effects that various switchgrass loadings have on Clostridium thermocellum solubilization and bioconversion are investigated. RESULTS Clostridium thermocellum was grown for 10 days on 10, 25, or 50 g/L switchgrass or Avicel at equivalent glucan loadings. Avicel was completely consumed at all loadings, but total cellulose solubilization decreased from 63 to 37% as switchgrass loadings increased from 10 to 50 g/L. Washed, spent switchgrass could be additionally hydrolyzed and fermented in second-round fermentations suggesting that access to fermentable substrates was not the limiting factor at higher feedstock loadings. Results from fermentations on Avicel or cellobiose using culture medium supplemented with 50% spent fermentation broth demonstrated that compounds present in the supernatants from the 25 or 50 g/L switchgrass loadings were the most inhibitory to continued fermentation. CONCLUSIONS Recalcitrance alone cannot fully account for differences in solubilization and end-product formation between switchgrass and Avicel at increased substrate loadings. Experiments aimed at separating metabolic inhibition from inhibition of hydrolysis suggest that C. thermocellum's hydrolytic machinery is more vulnerable to inhibition from switchgrass-derived compounds than its fermentative metabolism.
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Affiliation(s)
- Tobin J. Verbeke
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 USA
- Present Address: Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4 Canada
| | - Gabriela M. Garcia
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 USA
| | - James G. Elkins
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 USA
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19
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Akinosho H, Yee K, Rodriguez M, Muchero W, Yoo CG, Li M, Thompson O, Pu Y, Brown S, Mielenz J, Ragauskas AJ. Lignin Exhibits Recalcitrance‐Associated Features Following the Consolidated Bioprocessing of
Populus trichocarpa
Natural Variants. ChemistrySelect 2017. [DOI: 10.1002/slct.201701572] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Hannah Akinosho
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
- Department of Chemistry and Biochemistry, G eorgia Institute of Technology Atlanta GA 30332
| | - Kelsey Yee
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Miguel Rodriguez
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Wellington Muchero
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Chang Geun Yoo
- Department of Chemical and Biomolecular Engineering & Department of Forestry Center for Renewable Carbon at Wildlife, and Fisheries University of Tennessee Knoxville TN 37996
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Mi Li
- Department of Chemical and Biomolecular Engineering & Department of Forestry Center for Renewable Carbon at Wildlife, and Fisheries University of Tennessee Knoxville TN 37996
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Olivia Thompson
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Yunqiao Pu
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Steven Brown
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Johnathan Mielenz
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
| | - Arthur J. Ragauskas
- Department of Chemical and Biomolecular Engineering & Department of Forestry Center for Renewable Carbon at Wildlife, and Fisheries University of Tennessee Knoxville TN 37996
- BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge TN 37831
- Biosciences Division Oak Ridge National Laboratory Oak Ridge TN 37831
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Anaerobic microplate assay for direct microbial conversion of switchgrass and Avicel using Clostridium thermocellum. Biotechnol Lett 2017; 40:303-308. [PMID: 29124514 PMCID: PMC5813073 DOI: 10.1007/s10529-017-2467-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 10/26/2017] [Indexed: 02/07/2023]
Abstract
OBJECTIVE To develop and prototype a high-throughput microplate assay to assess anaerobic microorganisms and lignocellulosic biomasses in a rapid, cost-effective screen for consolidated bioprocessing potential. RESULTS Clostridium thermocellum parent Δhpt strain deconstructed Avicel to cellobiose, glucose, and generated lactic acid, formic acid, acetic acid and ethanol as fermentation products in titers and ratios similar to larger scale fermentations confirming the suitability of a plate-based method for C. thermocellum growth studies. C. thermocellum strain LL1210, with gene deletions in the key central metabolic pathways, produced higher ethanol titers in the Consolidated Bioprocessing (CBP) plate assay for both Avicel and switchgrass fermentations when compared to the Δhpt strain. CONCLUSION A prototype microplate assay system is developed that will facilitate high-throughput bioprospecting for new lignocellulosic biomass types, genetic variants and new microbial strains for bioethanol production.
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Bioavailability of Carbohydrate Content in Natural and Transgenic Switchgrasses for the Extreme Thermophile Caldicellulosiruptor bescii. Appl Environ Microbiol 2017. [PMID: 28625990 DOI: 10.1128/aem.00969-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Improving access to the carbohydrate content of lignocellulose is key to reducing recalcitrance for microbial deconstruction and conversion to fuels and chemicals. Caldicellulosiruptor bescii completely solubilizes naked microcrystalline cellulose, yet this transformation is impeded within the context of the plant cell wall by a network of lignin and hemicellulose. Here, the bioavailability of carbohydrates to C. bescii at 70°C was examined for reduced lignin transgenic switchgrass lines COMT3(+) and MYB Trans, their corresponding parental lines (cultivar Alamo) COMT3(-) and MYB wild type (WT), and the natural variant cultivar Cave-in-Rock (CR). Transgenic modification improved carbohydrate solubilization by C. bescii to 15% (2.3-fold) for MYB and to 36% (1.5-fold) for COMT, comparable to the levels achieved for the natural variant, CR (36%). Carbohydrate solubilization was nearly doubled after two consecutive microbial fermentations compared to one microbial step, but it never exceeded 50% overall. Hydrothermal treatment (180°C) prior to microbial steps improved solubilization 3.7-fold for the most recalcitrant line (MYB WT) and increased carbohydrate recovery to nearly 50% for the least recalcitrant lines [COMT3(+) and CR]. Alternating microbial and hydrothermal steps (T→M→T→M) further increased bioavailability, achieving carbohydrate solubilization ranging from 50% for MYB WT to above 70% for COMT3(+) and CR. Incomplete carbohydrate solubilization suggests that cellulose in the highly lignified residue was inaccessible; indeed, residue from the T→M→T→M treatment was primarily glucan and inert materials (lignin and ash). While C. bescii could significantly solubilize the transgenic switchgrass lines and natural variant tested here, additional or alternative strategies (physical, chemical, enzymatic, and/or genetic) are needed to eliminate recalcitrance.IMPORTANCE Key to a microbial process for solubilization of plant biomass is the organism's access to the carbohydrate content of lignocellulose. Economically viable routes will characteristically minimize physical, chemical, and biological pretreatment such that microbial steps contribute to the greatest extent possible. Recently, transgenic versions of plants and trees have been developed with the intention of lowering the barrier to lignocellulose conversion, with particular focus on lignin content and composition. Here, the extremely thermophilic bacterium Caldicellulosiruptor bescii was used to solubilize natural and genetically modified switchgrass lines, with and without the aid of hydrothermal treatment. For lignocellulose conversion, it is clear that the microorganism, plant biomass substrate, and processing steps must all be considered simultaneously to achieve optimal results. Whether switchgrass lines engineered for low lignin or natural variants with desirable properties are used, conversion will depend on microbial access to crystalline cellulose in the plant cell wall.
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22
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Gao C, Liu L, Yang F. Development of a novel proton exchange membrane-free integrated MFC system with electric membrane bioreactor and air contact oxidation bed for efficient and energy-saving wastewater treatment. BIORESOURCE TECHNOLOGY 2017; 238:472-483. [PMID: 28475989 DOI: 10.1016/j.biortech.2017.04.086] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 04/18/2017] [Accepted: 04/21/2017] [Indexed: 06/07/2023]
Abstract
A novel combined system integrating MFC and electric membrane bioreactor (EMBR) was developed, in which a quartz sand chamber (QSC) was used, replacing expensive proton exchange membrane (PEM). An air contact oxidation bed (ACOB) and embedded trickling filter (TF) with filled volcano rock, was designed to increase dissolved oxygen (DO) in cathodic EMBR to save aeration cost. Membrane fouling in EMBR was successful inhibited/reduced by the generated bioelectricity of the system. The combined system demonstrated superior effluent quality in removing chemical oxygen demand (>97%) and ammonia nitrogen (>93%) during the stable operation, and the phosphorus removal was about 50%. Dominant bacteria (Nitrosomonas sp.; Comamonas sp.; Candidatus Kuenenia) played important roles in the removal of organic matter and ammonia nitrogen. The system has good application prospects in the efficient use of water and the development of sustainable wastewater recycling technology.
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Affiliation(s)
- Changfei Gao
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science & Technology, Dalian University of Technology, Dalian 116024, China
| | - Lifen Liu
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science & Technology, Dalian University of Technology, Dalian 116024, China; School of Food and Environment, Dalian University of Technology, Panjin 124221, China.
| | - Fenglin Yang
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science & Technology, Dalian University of Technology, Dalian 116024, China
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23
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Özparpucu M, Rüggeberg M, Gierlinger N, Cesarino I, Vanholme R, Boerjan W, Burgert I. Unravelling the impact of lignin on cell wall mechanics: a comprehensive study on young poplar trees downregulated for CINNAMYL ALCOHOL DEHYDROGENASE (CAD). THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 91:480-490. [PMID: 28440915 DOI: 10.1111/tpj.13584] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 04/18/2017] [Indexed: 05/18/2023]
Abstract
Lignin engineering is a promising tool to reduce the energy input and the need of chemical pre-treatments for the efficient conversion of plant biomass into fermentable sugars for downstream applications. At the same time, lignin engineering can offer new insight into the structure-function relationships of plant cell walls by combined mechanical, structural and chemical analyses. Here, this comprehensive approach was applied to poplar trees (Populus tremula × Populus alba) downregulated for CINNAMYL ALCOHOL DEHYDROGENASE (CAD) in order to gain insight into the impact of lignin reduction on mechanical properties. The downregulation of CAD resulted in a significant decrease in both elastic modulus and yield stress. As wood density and cellulose microfibril angle (MFA) did not show any significant differences between the wild type and the transgenic lines, these structural features could be excluded as influencing factors. Fourier transform infrared spectroscopy (FTIR) and Raman imaging were performed to elucidate changes in the chemical composition directly on the mechanically tested tissue sections. Lignin content was identified as a mechanically relevant factor, as a correlation with a coefficient of determination (r²) of 0.65 between lignin absorbance (as an indicator of lignin content) and tensile stiffness was found. A comparison of the present results with those of previous investigations shows that the mechanical impact of lignin alteration under tensile stress depends on certain structural conditions, such as a high cellulose MFA, which emphasizes the complex relationship between the chemistry and mechanical properties in plant cell walls.
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Affiliation(s)
- Merve Özparpucu
- Institute for Building Materials (IfB), ETH Zurich, 8093, Zurich, Switzerland
- Laboratory of Applied Wood Materials, Empa, 8600, Dübendorf, Switzerland
| | - Markus Rüggeberg
- Institute for Building Materials (IfB), ETH Zurich, 8093, Zurich, Switzerland
- Laboratory of Applied Wood Materials, Empa, 8600, Dübendorf, Switzerland
| | - Notburga Gierlinger
- Department of Nanobiotechnology, Institute for Biophysics, University of Natural Resources and Life Sciences Vienna, 1190, Wien, Austria
| | - Igor Cesarino
- Department of Botany, Institute of Biosciences, University of São Paulo, São Paulo, SP, Brazil
| | - Ruben Vanholme
- Department of Plant Biotechnology and Bioinformatics, Technologiepark 927, Ghent University, 9052, Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052, Ghent, Belgium
| | - Wout Boerjan
- Department of Plant Biotechnology and Bioinformatics, Technologiepark 927, Ghent University, 9052, Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052, Ghent, Belgium
| | - Ingo Burgert
- Institute for Building Materials (IfB), ETH Zurich, 8093, Zurich, Switzerland
- Laboratory of Applied Wood Materials, Empa, 8600, Dübendorf, Switzerland
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24
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Generation and Characterization of Acid Tolerant Fibrobacter succinogenes S85. Sci Rep 2017; 7:2277. [PMID: 28536480 PMCID: PMC5442110 DOI: 10.1038/s41598-017-02628-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 04/20/2017] [Indexed: 01/13/2023] Open
Abstract
Microorganisms are key components for plant biomass breakdown within rumen environments. Fibrobacter succinogenes have been identified as being active and dominant cellulolytic members of the rumen. In this study, F. succinogenes type strain S85 was adapted for steady state growth in continuous culture at pH 5.75 and confirmed to grow in the range of pH 5.60–5.65, which is lower than has been reported previously. Wild type and acid tolerant strains digested corn stover with equal efficiency in batch culture at low pH. RNA-seq analysis revealed 268 and 829 genes were differentially expressed at pH 6.10 and 5.65 compared to pH 6.70, respectively. Resequencing analysis identified seven single nucleotide polymorphisms (SNPs) in the sufD, yidE, xylE, rlmM, mscL and dosC genes of acid tolerant strains. Due to the absence of a F. succinogenes genetic system, homologues in Escherichia coli were mutated and complemented and the resulting strains were assayed for acid survival. Complementation with wild-type or acid tolerant F. succinogenes sufD restored E. coli wild-type levels of acid tolerance, suggesting a possible role in acid homeostasis. Recent genetic engineering developments need to be adapted and applied in F. succinogenes to further our understanding of this bacterium.
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25
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Tolbert AK, Yoo CG, Ragauskas AJ. Understanding the Changes to Biomass Surface Characteristics after Ammonia and Organosolv Pretreatments by Using Time-of-Flight Secondary-Ion Mass Spectrometry (TOF-SIMS). Chempluschem 2017; 82:686-690. [PMID: 31961521 DOI: 10.1002/cplu.201700138] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Indexed: 11/08/2022]
Abstract
Surface characteristic changes to poplar after ammonia and organosolv pretreatments were investigated by means of time-of-flight secondary-ion mass spectrometry (TOF-SIMS) analysis. Whereas normalized total polysaccharides and lignin contents on the surface differed from bulk chemical compositions, the surface cellulose ions detected by TOF-SIMS showed the same value trend as the cellulose content in the biomass. In addition, the lignin syringyl/guaiacyl ratio according to TOF-SIMS results showed the same trend as the ratio measured by means of NMR spectroscopic analysis, even though the ratio scales for each method were different. A similar correlation was determined between the surface cellulose and glucose release after enzymatic hydrolysis. These results demonstrate that surface characterization using TOF-SIMS can provide important information about the effects of pretreatment on biomass properties and its hydrolysis.
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Affiliation(s)
- Allison K Tolbert
- School of Chemistry and Biochemistry & Renewable Bioproducts Institute, Georgia Institute of Technology, Atlanta, GA, 30332, USA.,BioEnergy Science Center (BESC), Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Chang Geun Yoo
- BioEnergy Science Center (BESC), Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA.,UT-ORNL Joint Institute of Biological Science, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Arthur J Ragauskas
- BioEnergy Science Center (BESC), Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA.,UT-ORNL Joint Institute of Biological Science, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.,Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996, USA.,Center of Renewable Carbon, Department of Forestry, Wildlife, and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, TN, 37996, USA
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26
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Blumer-Schuette SE, Zurawski JV, Conway JM, Khatibi P, Lewis DL, Li Q, Chiang VL, Kelly RM. Caldicellulosiruptor saccharolyticus transcriptomes reveal consequences of chemical pretreatment and genetic modification of lignocellulose. Microb Biotechnol 2017; 10:1546-1557. [PMID: 28322023 PMCID: PMC5658599 DOI: 10.1111/1751-7915.12494] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Revised: 11/28/2016] [Accepted: 11/29/2016] [Indexed: 11/28/2022] Open
Abstract
Recalcitrance of plant biomass is a major barrier for commercially feasible cellulosic biofuel production. Chemical and enzymatic assays have been developed to measure recalcitrance and carbohydrate composition; however, none of these assays can directly report which polysaccharides a candidate microbe will sense during growth on these substrates. Here, we propose using the transcriptomic response of the plant biomass‐deconstructing microbe, Caldicellulosiruptor saccharolyticus, as a direct measure of how suitable a sample of plant biomass may be for fermentation based on the bioavailability of polysaccharides. Key genes were identified using the global gene response of the microbe to model plant polysaccharides and various types of unpretreated, chemically pretreated and genetically modified plant biomass. While the majority of C. saccharolyticus genes responding were similar between plant biomasses; subtle differences were discernable, most importantly between chemically pretreated or genetically modified biomass that both exhibit similar levels of solubilization by the microbe. Furthermore, the results here present a new paradigm for assessing plant–microbe interactions that can be deployed as a biological assay to report on the complexity and recalcitrance of plant biomass.
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Affiliation(s)
- Sara E Blumer-Schuette
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA
| | - Jeffrey V Zurawski
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA
| | - Jonathan M Conway
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA
| | - Piyum Khatibi
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA
| | - Derrick L Lewis
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA
| | - Quanzi Li
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, 27695, USA
| | - Vincent L Chiang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, 27695, USA
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA
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27
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Dumitrache A, Klingeman DM, Natzke J, Rodriguez M, Giannone RJ, Hettich RL, Davison BH, Brown SD. Specialized activities and expression differences for Clostridium thermocellum biofilm and planktonic cells. Sci Rep 2017; 7:43583. [PMID: 28240279 PMCID: PMC5327387 DOI: 10.1038/srep43583] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/25/2017] [Indexed: 01/01/2023] Open
Abstract
Clostridium (Ruminiclostridium) thermocellum is a model organism for its ability to deconstruct plant biomass and convert the cellulose into ethanol. The bacterium forms biofilms adherent to lignocellulosic feedstocks in a continuous cell-monolayer in order to efficiently break down and uptake cellulose hydrolysates. We developed a novel bioreactor design to generate separate sessile and planktonic cell populations for omics studies. Sessile cells had significantly greater expression of genes involved in catabolism of carbohydrates by glycolysis and pyruvate fermentation, ATP generation by proton gradient, the anabolism of proteins and lipids and cellular functions critical for cell division consistent with substrate replete conditions. Planktonic cells had notably higher gene expression for flagellar motility and chemotaxis, cellulosomal cellulases and anchoring scaffoldins, and a range of stress induced homeostasis mechanisms such as oxidative stress protection by antioxidants and flavoprotein co-factors, methionine repair, Fe-S cluster assembly and repair in redox proteins, cell growth control through tRNA thiolation, recovery of damaged DNA by nucleotide excision repair and removal of terminal proteins by proteases. This study demonstrates that microbial attachment to cellulose substrate produces widespread gene expression changes for critical functions of this organism and provides physiological insights for two cells populations relevant for engineering of industrially-ready phenotypes.
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Affiliation(s)
- Alexandru Dumitrache
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Dawn M Klingeman
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Jace Natzke
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Miguel Rodriguez
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Richard J Giannone
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Robert L Hettich
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Brian H Davison
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
| | - Steven D Brown
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, U.S.A
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28
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Li M, Pu Y, Yoo CG, Gjersing E, Decker SR, Doeppke C, Shollenberger T, Tschaplinski TJ, Engle NL, Sykes RW, Davis MF, Baxter HL, Mazarei M, Fu C, Dixon RA, Wang ZY, Neal Stewart C, Ragauskas AJ. Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:12. [PMID: 28053668 PMCID: PMC5209956 DOI: 10.1186/s13068-016-0695-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 12/23/2016] [Indexed: 05/22/2023]
Abstract
BACKGROUND The native recalcitrance of plants hinders the biomass conversion process using current biorefinery techniques. Down-regulation of the caffeic acid O-methyltransferase (COMT) gene in the lignin biosynthesis pathway of switchgrass reduced the thermochemical and biochemical conversion recalcitrance of biomass. Due to potential environmental influences on lignin biosynthesis and deposition, studying the consequences of physicochemical changes in field-grown plants without pretreatment is essential to evaluate the performance of lignin-altered plants. We determined the chemical composition, cellulose crystallinity and the degree of its polymerization, molecular weight of hemicellulose, and cellulose accessibility of cell walls in order to better understand the fundamental features of why biomass is recalcitrant to conversion without pretreatment. The most important is to investigate whether traits and features are stable in the dynamics of field environmental effects over multiple years. RESULTS Field-grown COMT down-regulated plants maintained both reduced cell wall recalcitrance and lignin content compared with the non-transgenic controls for at least 3 seasons. The transgenic switchgrass yielded 35-84% higher total sugar release (enzymatic digestibility or saccharification) from a 72-h enzymatic hydrolysis without pretreatment and also had a 25-32% increase in enzymatic sugar release after hydrothermal pretreatment. The COMT-silenced switchgrass lines had consistently lower lignin content, e.g., 12 and 14% reduction for year 2 and year 3 growing season, respectively, than the control plants. By contrast, the transgenic lines had 7-8% more xylan and galactan contents than the wild-type controls. Gel permeation chromatographic results revealed that the weight-average molecular weights of hemicellulose were 7-11% lower in the transgenic than in the control lines. In addition, we found that silencing of COMT in switchgrass led to 20-22% increased cellulose accessibility as measured by the Simons' stain protocol. No significant changes were observed on the arabinan and glucan contents, cellulose crystallinity, and cellulose degree of polymerization between the transgenic and control plants. With the 2-year comparative analysis, both the control and transgenic lines had significant increases in lignin and glucan contents and hemicellulose molecular weight across the growing seasons. CONCLUSIONS The down-regulation of COMT in switchgrass resulting in a reduced lignin content and biomass recalcitrance is stable in a field-grown trial for at least three seasons. Among the determined affecting factors, the reduced biomass recalcitrance of the COMT-silenced switchgrass, grown in the field conditions for two and three seasons, was likely related to the decreased lignin content and increased biomass accessibility, whereas the cellulose crystallinity and degree of its polymerization and hemicellulose molecular weights did not contribute to the reduction of recalcitrance significantly. This finding suggests that lignin down-regulation in lignocellulosic feedstock confers improved saccharification that translates from greenhouse to field trial and that lignin content and biomass accessibility are two significant factors for developing a reduced recalcitrance feedstock by genetic modification.
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Affiliation(s)
- Mi Li
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Yunqiao Pu
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Chang Geun Yoo
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Erica Gjersing
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Stephen R. Decker
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Crissa Doeppke
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Todd Shollenberger
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Timothy J. Tschaplinski
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Nancy L. Engle
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | | | | | - Holly L. Baxter
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Department of Plant Sciences, University of Tennessee, Knoxville, TN USA
| | - Mitra Mazarei
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Department of Plant Sciences, University of Tennessee, Knoxville, TN USA
| | - Chunxiang Fu
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK USA
| | - Richard A. Dixon
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioDiscovery Institute and Department of Biological Sciences, University of North Texas, Denton, TX USA
| | - Zeng-Yu Wang
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK USA
| | - C. Neal Stewart
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Department of Plant Sciences, University of Tennessee, Knoxville, TN USA
| | - Arthur J. Ragauskas
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
- Department of Chemical and Biomolecular Engineering & Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN USA
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29
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Agrawal R, Satlewal A, Kapoor M, Mondal S, Basu B. Investigating the enzyme-lignin binding with surfactants for improved saccharification of pilot scale pretreated wheat straw. BIORESOURCE TECHNOLOGY 2017; 224:411-418. [PMID: 27847236 DOI: 10.1016/j.biortech.2016.11.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 10/28/2016] [Accepted: 11/01/2016] [Indexed: 05/11/2023]
Abstract
In this study, commercial surfactants have been investigated at economically viable dosage to enhance the enzymatic saccharification of pretreated wheat straw at high solid loadings. Twenty one surfactants were evaluated with pilot scale pretreated wheat straw and mechanism of surfactant action has been elucidated. One surfactant has improved the saccharification of dilute acid wheat straw (DAWS) by 26.4% after 24h and 23.1% after 48h while, steam exploded wheat straw (SEWS) saccharification was increased by 51.2% after 24h and 36.4% after 48h at 10% solid loading. At 20% solid loading, about 31% increase in yield was obtained on DAWS and about 55% on SEWS after 48h. Further, lignin was isolated from pretreated wheat straws and characterized which revealed that SEWS derived lignin was more hydrophobic than DAWS lignin. This investigation suggests that surfactant supplementation during saccharification is an effective strategy to achieve higher saccharification yield.
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Affiliation(s)
- Ruchi Agrawal
- DBT-IOC Centre for Advanced Bioenergy Research, Research and Development Centre, Indian Oil Corporation Ltd., Sector-13, Faridabad 121007, India
| | - Alok Satlewal
- DBT-IOC Centre for Advanced Bioenergy Research, Research and Development Centre, Indian Oil Corporation Ltd., Sector-13, Faridabad 121007, India.
| | - Manali Kapoor
- DBT-IOC Centre for Advanced Bioenergy Research, Research and Development Centre, Indian Oil Corporation Ltd., Sector-13, Faridabad 121007, India
| | - Sujit Mondal
- Analytical Department, Research and Development Centre, Indian Oil Corporation Ltd., Sector-13, Faridabad 121007, India
| | - Biswajit Basu
- DBT-IOC Centre for Advanced Bioenergy Research, Research and Development Centre, Indian Oil Corporation Ltd., Sector-13, Faridabad 121007, India
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30
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Poudel S, Giannone RJ, Rodriguez M, Raman B, Martin MZ, Engle NL, Mielenz JR, Nookaew I, Brown SD, Tschaplinski TJ, Ussery D, Hettich RL. Integrated omics analyses reveal the details of metabolic adaptation of Clostridium thermocellum to lignocellulose-derived growth inhibitors released during the deconstruction of switchgrass. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:14. [PMID: 28077967 PMCID: PMC5223564 DOI: 10.1186/s13068-016-0697-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 12/24/2016] [Indexed: 05/03/2023]
Abstract
BACKGROUND Clostridium thermocellum is capable of solubilizing and converting lignocellulosic biomass into ethanol. Although much of the work-to-date has centered on characterizing this microbe's growth on model cellulosic substrates, such as cellobiose, Avicel, or filter paper, it is vitally important to understand its metabolism on more complex, lignocellulosic substrates to identify relevant industrial bottlenecks that could undermine efficient biofuel production. To this end, we have examined a time course progression of C. thermocellum grown on switchgrass to assess the metabolic and protein changes that occur during the conversion of plant biomass to ethanol. RESULTS The most striking feature of the metabolome was the observed accumulation of long-chain, branched fatty acids over time, implying an adaptive restructuring of C. thermocellum's cellular membrane as the culture progresses. This is undoubtedly a response to the gradual accumulation of lignocellulose-derived inhibitory compounds as the organism deconstructs the switchgrass to access the embedded cellulose. Corroborating the metabolomics data, proteomic analysis revealed a corresponding time-dependent increase in various enzymes, including those involved in the interconversion of branched amino acids valine, leucine, and isoleucine to iso- and anteiso-fatty acid precursors. Additionally, the metabolic accumulation of hemicellulose-derived sugars and sugar alcohols concomitant with increased abundance of enzymes involved in C5 sugar metabolism/pentose phosphate pathway indicates that C. thermocellum shifts glycolytic intermediates to alternate pathways to modulate overall carbon flux in response to C5 sugar metabolites that increase during lignocellulose deconstruction. CONCLUSIONS Integrated omic platforms provided complementary systems biological information that highlight C. thermocellum's specific response to cytotoxic inhibitors released during the deconstruction and utilization of switchgrass. These additional viewpoints allowed us to fully realize the level to which the organism adapts to an increasingly challenging culture environment-information that will prove critical to C. thermocellum's industrial efficacy.
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Affiliation(s)
- Suresh Poudel
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
- Department of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996 USA
| | | | - Miguel Rodriguez
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
| | - Babu Raman
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
- Dow AgroSciences, 9330 Zionsville Road, Indianapolis, IN 46268 USA
| | - Madhavi Z. Martin
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
| | - Nancy L. Engle
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
| | | | - Intawat Nookaew
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
- Department of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, AR 72205 USA
| | - Steven D. Brown
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
- Department of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996 USA
| | | | - David Ussery
- Biosciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
- Department of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, AR 72205 USA
| | - Robert L. Hettich
- Chemical Sciences Division, Oak Ridge National Lab, Oak Ridge, TN 37831 USA
- Department of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996 USA
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31
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Singh N, Mathur AS, Tuli DK, Gupta RP, Barrow CJ, Puri M. Cellulosic ethanol production via consolidated bioprocessing by a novel thermophilic anaerobic bacterium isolated from a Himalayan hot spring. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:73. [PMID: 28344648 PMCID: PMC5361838 DOI: 10.1186/s13068-017-0756-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 03/10/2017] [Indexed: 05/07/2023]
Abstract
BACKGROUND Cellulose-degrading thermophilic anaerobic bacterium as a suitable host for consolidated bioprocessing (CBP) has been proposed as an economically suited platform for the production of second-generation biofuels. To recognize the overall objective of CBP, fermentation using co-culture of different cellulolytic and sugar-fermenting thermophilic anaerobic bacteria has been widely studied as an approach to achieving improved ethanol production. We assessed monoculture and co-culture fermentation of novel thermophilic anaerobic bacterium for ethanol production from real substrates under controlled conditions. RESULTS In this study, Clostridium sp. DBT-IOC-C19, a cellulose-degrading thermophilic anaerobic bacterium, was isolated from the cellulolytic enrichment cultures obtained from a Himalayan hot spring. Strain DBT-IOC-C19 exhibited a broad substrate spectrum and presented single-step conversion of various cellulosic and hemicellulosic substrates to ethanol, acetate, and lactate with ethanol being the major fermentation product. Additionally, the effect of varying cellulose concentrations on the fermentation performance of the strain was studied, indicating a maximum cellulose utilization ability of 10 g L-1 cellulose. Avicel degradation kinetics of the strain DBT-IOC-C19 displayed 94.6% degradation at 5 g L-1 and 82.74% degradation at 10 g L-1 avicel concentration within 96 h of fermentation. In a comparative study with Clostridium thermocellum DSM 1313, the ethanol and total product concentrations were higher by the newly isolated strain on pretreated rice straw at an equivalent substrate loading. Three different co-culture combinations were used on various substrates that presented two-fold yield improvement than the monoculture during batch fermentation. CONCLUSIONS This study demonstrated the direct fermentation ability of the novel thermophilic anaerobic bacteria on various cellulosic and hemicellulosic substrates into ethanol without the aid of any exogenous enzymes, representing CBP-based fermentation approach. Here, the broad substrate utilization spectrum of isolated cellulolytic thermophilic anaerobic bacterium was shown to be of potential utility. We demonstrated that the co-culture strategy involving novel strains is efficient in improving ethanol production from real substrate.
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Affiliation(s)
- Nisha Singh
- Bioprocessing Laboratory, Centre for Chemistry and Biotechnology, Deakin University, Waurn Ponds, VIC 3217 Australia
- DBT-IOC Centre for Advance Bioenergy Research, Research & Development Centre, Indian Oil Corporation Limited, Sector-13, Faridabad, 121007 India
| | - Anshu S. Mathur
- DBT-IOC Centre for Advance Bioenergy Research, Research & Development Centre, Indian Oil Corporation Limited, Sector-13, Faridabad, 121007 India
| | - Deepak K. Tuli
- DBT-IOC Centre for Advance Bioenergy Research, Research & Development Centre, Indian Oil Corporation Limited, Sector-13, Faridabad, 121007 India
| | - Ravi. P. Gupta
- DBT-IOC Centre for Advance Bioenergy Research, Research & Development Centre, Indian Oil Corporation Limited, Sector-13, Faridabad, 121007 India
| | - Colin J. Barrow
- Bioprocessing Laboratory, Centre for Chemistry and Biotechnology, Deakin University, Waurn Ponds, VIC 3217 Australia
| | - Munish Puri
- Bioprocessing Laboratory, Centre for Chemistry and Biotechnology, Deakin University, Waurn Ponds, VIC 3217 Australia
- Centre for Marine Bioproducts Development, Medical Biotechnology, Flinders University, Adelaide, Australia
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