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Golin AP, Choi D, Ghahary A. Hand sanitizers: A review of ingredients, mechanisms of action, modes of delivery, and efficacy against coronaviruses. Am J Infect Control 2020; 48:1062-1067. [PMID: 32565272 PMCID: PMC7301780 DOI: 10.1016/j.ajic.2020.06.182] [Citation(s) in RCA: 107] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/14/2020] [Accepted: 06/15/2020] [Indexed: 12/13/2022]
Abstract
Background The emergence of the novel virus, SARS-CoV-2, has posed unprecedented challenges to public health around the world. Currently, strategies to deal with COVID-19 are purely supportive and preventative, aimed at reducing transmission. An effective and simple method for reducing transmission of infections in public or healthcare settings is hand hygiene. Unfortunately, little is known regarding the efficacy of hand sanitizers against SARS-CoV-2. Methods In this review, an extensive literature search was performed to succinctly summarize the primary active ingredients and mechanisms of action of hand sanitizers, compare the effectiveness and compliance of gel and foam sanitizers, and predict whether alcohol and non-alcohol hand sanitizers would be effective against SARS-CoV-2. Results Most alcohol-based hand sanitizers are effective at inactivating enveloped viruses, including coronaviruses. With what is currently known in the literature, one may not confidently suggest one mode of hand sanitizing delivery over the other. When hand washing with soap and water is unavailable, a sufficient volume of sanitizer is necessary to ensure complete hand coverage, and compliance is critical for appropriate hand hygiene. Conclusions By extrapolating effectiveness of hand sanitizers on viruses of similar structure to SARS-CoV-2, this virus should be effectively inactivated with current hand hygiene products, though future research should attempt to determine this directly.
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Pidot SJ, Gao W, Buultjens AH, Monk IR, Guerillot R, Carter GP, Lee JYH, Lam MMC, Grayson ML, Ballard SA, Mahony AA, Grabsch EA, Kotsanas D, Korman TM, Coombs GW, Robinson JO, Gonçalves da Silva A, Seemann T, Howden BP, Johnson PDR, Stinear TP. Increasing tolerance of hospital Enterococcus faecium to handwash alcohols. Sci Transl Med 2019; 10:10/452/eaar6115. [PMID: 30068573 DOI: 10.1126/scitranslmed.aar6115] [Citation(s) in RCA: 133] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 02/10/2018] [Accepted: 04/03/2018] [Indexed: 11/03/2022]
Abstract
Alcohol-based disinfectants and particularly hand rubs are a key way to control hospital infections worldwide. Such disinfectants restrict transmission of pathogens, such as multidrug-resistant Staphylococcus aureus and Enterococcus faecium Despite this success, health care infections caused by E. faecium are increasing. We tested alcohol tolerance of 139 hospital isolates of E. faecium obtained between 1997 and 2015 and found that E. faecium isolates after 2010 were 10-fold more tolerant to killing by alcohol than were older isolates. Using a mouse gut colonization model of E. faecium transmission, we showed that alcohol-tolerant E. faecium resisted standard 70% isopropanol surface disinfection, resulting in greater mouse gut colonization compared to alcohol-sensitive E. faecium We next looked for bacterial genomic signatures of adaptation. Alcohol-tolerant E. faecium accumulated mutations in genes involved in carbohydrate uptake and metabolism. Mutagenesis confirmed the roles of these genes in the tolerance of E. faecium to isopropanol. These findings suggest that bacterial adaptation is complicating infection control recommendations, necessitating additional procedures to prevent E. faecium from spreading in hospital settings.
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Affiliation(s)
- Sacha J Pidot
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Wei Gao
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Andrew H Buultjens
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Ian R Monk
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Romain Guerillot
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Glen P Carter
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Jean Y H Lee
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Margaret M C Lam
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - M Lindsay Grayson
- Infectious Diseases Department, Austin Health, Heidelberg, Victoria 3084, Australia.,Department of Medicine, University of Melbourne, Heidelberg, Victoria 3084, Australia.,Department of Epidemiology and Preventive Medicine, Monash University, Victoria 3800, Australia
| | - Susan A Ballard
- Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Andrew A Mahony
- Infectious Diseases Department, Austin Health, Heidelberg, Victoria 3084, Australia
| | - Elizabeth A Grabsch
- Infectious Diseases Department, Austin Health, Heidelberg, Victoria 3084, Australia
| | - Despina Kotsanas
- Monash Infectious Diseases, Monash Health, Clayton, Victoria 3168, Australia
| | - Tony M Korman
- Monash Infectious Diseases, Monash Health, Clayton, Victoria 3168, Australia
| | - Geoffrey W Coombs
- Antimicrobial Resistance and Infectious Diseases Research Laboratory, School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia.,Department of Microbiology, PathWest Laboratory Medicine WA, Fiona Stanley Hospital, Murdoch, Western Australia 6150, Australia
| | - J Owen Robinson
- Antimicrobial Resistance and Infectious Diseases Research Laboratory, School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia.,Department of Microbiology, PathWest Laboratory Medicine WA, Fiona Stanley Hospital, Murdoch, Western Australia 6150, Australia
| | - Anders Gonçalves da Silva
- Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Torsten Seemann
- Melbourne Bioinformatics, University of Melbourne, Carlton, Victoria 3053, Australia
| | - Benjamin P Howden
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia.,Infectious Diseases Department, Austin Health, Heidelberg, Victoria 3084, Australia.,Department of Medicine, University of Melbourne, Heidelberg, Victoria 3084, Australia.,Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia
| | - Paul D R Johnson
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia. .,Infectious Diseases Department, Austin Health, Heidelberg, Victoria 3084, Australia.,Department of Medicine, University of Melbourne, Heidelberg, Victoria 3084, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria 3010, Australia.
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Chi X, Li J, Wang X, Zhang Y, Antwi P. Hyper-production of butyric acid from delignified rice straw by a novel consolidated bioprocess. BIORESOURCE TECHNOLOGY 2018; 254:115-120. [PMID: 29413911 DOI: 10.1016/j.biortech.2018.01.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/07/2018] [Accepted: 01/08/2018] [Indexed: 06/08/2023]
Abstract
A novel consolidated bioprocess for hyper-production of butyric acid from delignified rice straw without exogenous enzymes involved was developed by co-fermentation of Clostridium thermocellum ATCC 27405 and C. thermobutyricum ATCC 49875. Feasibility of the consolidated bioprocess was approved by batch fermentations, with the optimum pH of 6.5. Fed-batch fermentation with a constant pH of 6.5 at 55 °C could enhance the butyric acid yield to a remarkable 33.9 g/L with a selectivity as high as 78%. Metabolic analysis of the co-culture indicated that sugars liberated by C. thermocellum ATCC 27405 were effectively converted to butyric acid by C. thermobutyricum ATCC 49875. Secondary metabolism of C. thermobutyricum ATCC 49875 also contributed to the hyper-production of butyric acid, resulting in the re-assimilation of by-products such as acetic acid and ethanol. This work provides a more effective fermentation process for butyric acid production from lignocellulosic biomass for future applications.
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Affiliation(s)
- Xue Chi
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, 73 Huanghe Road, Harbin 150090, China
| | - Jianzheng Li
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, 73 Huanghe Road, Harbin 150090, China.
| | - Xin Wang
- School of Resources and Environment, Northeast Agriculture University, 59 Mucai Road, Harbin 150001, China
| | - Yafei Zhang
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, 73 Huanghe Road, Harbin 150090, China
| | - Philip Antwi
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, 73 Huanghe Road, Harbin 150090, China
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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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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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6
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Sheng T, Zhao L, Gao LF, Liu WZ, Cui MH, Guo ZC, Ma XD, Ho SH, Wang AJ. Lignocellulosic saccharification by a newly isolated bacterium, Ruminiclostridium thermocellum M3 and cellular cellulase activities for high ratio of glucose to cellobiose. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:172. [PMID: 27525041 PMCID: PMC4982309 DOI: 10.1186/s13068-016-0585-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 07/27/2016] [Indexed: 05/25/2023]
Abstract
BACKGROUND Lignocellulosic biomass is one of earth's most abundant resources, and it has great potential for biofuel production because it is renewable and has carbon-neutral characteristics. Lignocellulose is mainly composed of carbohydrate polymers (cellulose and hemicellulose), which contain approximately 75 % fermentable sugars for biofuel fermentation. However, saccharification by cellulases is always the main bottleneck for commercialization. Compared with the enzyme systems of fungi, bacteria have evolved distinct systems to directly degrade lignocellulose. However, most reported bacterial saccharification is not efficient enough without help from additional β-glucosidases. Thus, to enhance the economic feasibility of using lignocellulosic biomass for biofuel production, it will be extremely important to develop a novel bacterial saccharification system that does not require the addition of β-glucosidases. RESULTS In this study, a new thermophilic bacterium named Ruminiclostridium thermocellum M3, which could directly saccharify lignocellulosic biomass, was isolated from horse manure. The results showed that R. thermocellum M3 can grow at 60 °C on a variety of carbon polymers, including microcrystalline cellulose, filter paper, and xylan. Upon utilization of these substrates, R. thermocellum M3 achieved an oligosaccharide yield of 481.5 ± 16.0 mg/g Avicel, and a cellular β-glucosidase activity of up to 0.38 U/mL, which is accompanied by a high proportion (approximately 97 %) of glucose during the saccharification. R. thermocellum M3 also showed potential in degrading natural lignocellulosic biomass, without additional pretreatment, to oligosaccharides, and the oligosaccharide yields using poplar sawdust, corn cobs, rice straw, and cornstalks were 52.7 ± 2.77, 77.8 ± 5.9, 89.4 ± 9.3, and 107.8 ± 5.88 mg/g, respectively. CONCLUSIONS The newly isolated strain R. thermocellum M3 degraded lignocellulose and accumulated oligosaccharides. R. thermocellum M3 saccharified lignocellulosic feedstock without the need to add β-glucosidases or control the pH, and the high proportion of glucose production distinguishes it from all other known monocultures of cellulolytic bacteria. R. thermocellum M3 is a potential candidate for lignocellulose saccharification, and it is a valuable choice for the refinement of bioproducts.
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Affiliation(s)
- Tao Sheng
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
| | - Lei Zhao
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
- Advanced Water Management Centre, Faculty of Engineering, Architecture and Information Technology, The University of Queensland, Brisbane, QLD 4072 Australia
| | - Ling-Fang Gao
- CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Wen-Zong Liu
- CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Min-Hua Cui
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
| | - Ze-Chong Guo
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
| | - Xiao-Dan Ma
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
| | - Shih-Hsin Ho
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
| | - Ai-Jie Wang
- State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090 China
- CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
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Dumitrache A, Akinosho H, Rodriguez M, Meng X, Yoo CG, Natzke J, Engle NL, Sykes RW, Tschaplinski TJ, Muchero W, Ragauskas AJ, Davison BH, Brown SD. Consolidated bioprocessing of Populus using Clostridium (Ruminiclostridium) thermocellum: a case study on the impact of lignin composition and structure. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:31. [PMID: 26855670 PMCID: PMC4743434 DOI: 10.1186/s13068-016-0445-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/20/2016] [Indexed: 05/04/2023]
Abstract
BACKGROUND Higher ratios of syringyl-to-guaiacyl (S/G) lignin components of Populus were shown to improve sugar release by enzymatic hydrolysis using commercial blends. Cellulolytic microbes are often robust biomass hydrolyzers and may offer cost advantages; however, it is unknown whether their activity can also be significantly influenced by the ratio of different monolignol types in Populus biomass. Hydrolysis and fermentation of autoclaved, but otherwise not pretreated Populus trichocarpa by Clostridium thermocellum ATCC 27405 was compared using feedstocks that had similar carbohydrate and total lignin contents but differed in S/G ratios. RESULTS Populus with an S/G ratio of 2.1 was converted more rapidly and to a greater extent compared to similar biomass that had a ratio of 1.2. For either microbes or commercial enzymes, an approximate 50 % relative difference in total solids solubilization was measured for both biomasses, which suggests that the differences and limitations in the microbial breakdown of lignocellulose may be largely from the enzymatic hydrolytic process. Surprisingly, the reduction in glucan content per gram solid in the residual microbially processed biomass was similar (17-18 %) irrespective of S/G ratio, pointing to a similar mechanism of solubilization that proceeded at different rates. Fermentation metabolome testing did not reveal the release of known biomass-derived alcohol and aldehyde inhibitors that could explain observed differences in microbial hydrolytic activity. Biomass-derived p-hydroxybenzoic acid was up to nine-fold higher in low S/G ratio biomass fermentations, but was not found to be inhibitory in subsequent test fermentations. Cellulose crystallinity and degree of polymerization did not vary between Populus lines and had minor changes after fermentation. However, lignin molecular weights and cellulose accessibility determined by Simons' staining were positively correlated to the S/G content. CONCLUSIONS Higher S/G ratios in Populus biomass lead to longer and more linear lignin chains and greater access to surface cellulosic content by microbe-bound enzymatic complexes. Substrate access limitation is suggested as a primary bottleneck in solubilization of minimally processed Populus, which has important implications for microbial deconstruction of lignocellulose biomass. Our findings will allow others to examine different Populus lines and to test if similar observations are possible for other plant species.
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Affiliation(s)
- Alexandru Dumitrache
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Hannah Akinosho
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />Renewable Bioproducts Institute, Georgia Institute of Technology, Atlanta, GA 30332 USA
- />UT-ORNL Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Miguel Rodriguez
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Xianzhi Meng
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />Renewable Bioproducts Institute, Georgia Institute of Technology, Atlanta, GA 30332 USA
- />School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332 USA
| | - Chang Geun Yoo
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />UT-ORNL Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Jace Natzke
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Nancy L. Engle
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Robert W. Sykes
- />National Renewable Energy Laboratory, US Department of Energy, Golden, CO 80401 USA
| | - Timothy J. Tschaplinski
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Wellington Muchero
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Arthur J. Ragauskas
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />UT-ORNL Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Department of Chemical and Biomolecular Engineering, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996 USA
| | - Brian H. Davison
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Steven D. Brown
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
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8
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Elimination of formate production in Clostridium thermocellum. J Ind Microbiol Biotechnol 2015; 42:1263-72. [PMID: 26162629 PMCID: PMC4536278 DOI: 10.1007/s10295-015-1644-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 06/15/2015] [Indexed: 02/05/2023]
Abstract
The ability of Clostridium thermocellum to rapidly degrade cellulose and ferment resulting hydrolysis products into ethanol makes it a promising platform organism for cellulosic biofuel production via consolidated bioprocessing. Currently, however, ethanol yield is far below theoretical maximum due to branched product pathways that divert carbon and electrons towards formate, H2, lactate, acetate, and secreted amino acids. To redirect carbon and electron flux away from formate, genes encoding pyruvate:formate lyase (pflB) and PFL-activating enzyme (pflA) were deleted. Formate production in the resulting Δpfl strain was eliminated and acetate production decreased by 50 % on both complex and defined medium. The growth rate of the Δpfl strain decreased by 2.9-fold on defined medium and biphasic growth was observed on complex medium. Supplementation of defined medium with 2 mM formate restored Δpfl growth rate to 80 % of the parent strain. The role of pfl in metabolic engineering strategies and C1 metabolism is discussed.
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Facultative Anaerobe Caldibacillus debilis GB1: Characterization and Use in a Designed Aerotolerant, Cellulose-Degrading Coculture with Clostridium thermocellum. Appl Environ Microbiol 2015; 81:5567-73. [PMID: 26048931 DOI: 10.1128/aem.00735-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 06/03/2015] [Indexed: 11/20/2022] Open
Abstract
Development of a designed coculture that can achieve aerotolerant ethanogenic biofuel production from cellulose can reduce the costs of maintaining anaerobic conditions during industrial consolidated bioprocessing (CBP). To this end, a strain of Caldibacillus debilis isolated from an air-tolerant cellulolytic consortium which included a Clostridium thermocellum strain was characterized and compared with the C. debilis type strain. Characterization of isolate C. debilis GB1 and comparisons with the type strain of C. debilis revealed significant physiological differences, including (i) the absence of anaerobic metabolism in the type strain and (ii) different end product synthesis profiles under the experimental conditions used. The designed cocultures displayed unique responses to oxidative conditions, including an increase in lactate production. We show here that when the two species were cultured together, the noncellulolytic facultative anaerobe C. debilis GB1 provided respiratory protection for C. thermocellum, allowing the synergistic utilization of cellulose even under an aerobic atmosphere.
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10
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Pradhan N, Dipasquale L, d'Ippolito G, Panico A, Lens PNL, Esposito G, Fontana A. Hydrogen Production by the Thermophilic Bacterium Thermotoga neapolitana. Int J Mol Sci 2015; 16:12578-600. [PMID: 26053393 PMCID: PMC4490462 DOI: 10.3390/ijms160612578] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 05/20/2015] [Accepted: 05/22/2015] [Indexed: 11/18/2022] Open
Abstract
As the only fuel that is not chemically bound to carbon, hydrogen has gained interest as an energy carrier to face the current environmental issues of greenhouse gas emissions and to substitute the depleting non-renewable reserves. In the last years, there has been a significant increase in the number of publications about the bacterium Thermotoga neapolitana that is responsible for production yields of H2 that are among the highest achievements reported in the literature. Here we present an extensive overview of the most recent studies on this hyperthermophilic bacterium together with a critical discussion of the potential of fermentative production by this bacterium. The review article is organized into sections focused on biochemical, microbiological and technical issues, including the effect of substrate, reactor type, gas sparging, temperature, pH, hydraulic retention time and organic loading parameters on rate and yield of gas production.
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Affiliation(s)
- Nirakar Pradhan
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Via Di Biasio, 43, 03043 Cassino, FR, Italy.
| | - Laura Dipasquale
- Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Via Campi Flegrei 34, 80078 Pozzuoli, Napoli, Italy.
| | - Giuliana d'Ippolito
- Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Via Campi Flegrei 34, 80078 Pozzuoli, Napoli, Italy.
| | - Antonio Panico
- Telematic University Pegaso, piazza Trieste e Trento, 48, 80132 Naples, Italy.
| | - Piet N L Lens
- UNESCO-IHE Institute for Water Education, Westvest 7, 2611-AX Delft, The Netherlands.
| | - Giovanni Esposito
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Via Di Biasio, 43, 03043 Cassino, FR, Italy.
| | - Angelo Fontana
- Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Via Campi Flegrei 34, 80078 Pozzuoli, Napoli, Italy.
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Tang H, Ou J, Zhu M. Development of a quantitative real-time PCR assay for direct detection of growth of cellulose-degrading bacterium Clostridium thermocellum
in lignocellulosic degradation. J Appl Microbiol 2015; 118:1333-44. [DOI: 10.1111/jam.12801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 02/28/2015] [Accepted: 03/13/2015] [Indexed: 12/01/2022]
Affiliation(s)
- H. Tang
- School of Bioscience and Bioengineering; South China University of Technology; Guangzhou China
| | - J.F. Ou
- School of Bioscience and Bioengineering; South China University of Technology; Guangzhou China
| | - M.J. Zhu
- School of Bioscience and Bioengineering; South China University of Technology; Guangzhou China
- State Key Laboratory of Pulp and Paper Engineering; South China University of Technology; Guangzhou China
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering; South China University of Technology; Guangzhou China
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Optimization of influential nutrients during direct cellulose fermentation into hydrogen by Clostridium thermocellum. Int J Mol Sci 2015; 16:3116-32. [PMID: 25647413 PMCID: PMC4346883 DOI: 10.3390/ijms16023116] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/22/2015] [Accepted: 01/27/2015] [Indexed: 11/18/2022] Open
Abstract
Combinatorial effects of influential growth nutrients were investigated in order to enhance hydrogen (H2) production during direct conversion of cellulose by Clostridium thermocellum DSM 1237. A central composite face-centered design and response surface methodology (RSM) were applied to optimize concentrations of cellulose, yeast extract (YE), and magnesium chloride (Mg) in culture. The overall optimum composition generated by the desirability function resulted in 57.28 mmol H2/L-culture with 1.30 mol H2/mol glucose and 7.48 mmol/(g·cell·h) when cultures contained 25 g/L cellulose, 2 g/L YE, and 1.75 g/L Mg. Compared with the unaltered medium, the optimized medium produced approximately 3.2-fold more H2 within the same time-frame with 50% higher specific productivity, which are also better than previously reported values from similar studies. Nutrient composition that diverted carbon and electron flux away from H2 promoting ethanol production was also determined. This study represents the first investigation dealing with multifactor optimization with RSM for H2 production during direct cellulose fermentation.
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Akinosho H, Yee K, Close D, Ragauskas A. The emergence of Clostridium thermocellum as a high utility candidate for consolidated bioprocessing applications. Front Chem 2014; 2:66. [PMID: 25207268 PMCID: PMC4143619 DOI: 10.3389/fchem.2014.00066] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 07/28/2014] [Indexed: 01/25/2023] Open
Abstract
First isolated in 1926, Clostridium thermocellum has recently received increased attention as a high utility candidate for use in consolidated bioprocessing (CBP) applications. These applications, which seek to process lignocellulosic biomass directly into useful products such as ethanol, are gaining traction as economically feasible routes toward the production of fuel and other high value chemical compounds as the shortcomings of fossil fuels become evident. This review evaluates C. thermocellum's role in this transitory process by highlighting recent discoveries relating to its genomic, transcriptomic, proteomic, and metabolomic responses to varying biomass sources, with a special emphasis placed on providing an overview of its unique, multivariate enzyme cellulosome complex and the role that this structure performs during biomass degradation. Both naturally evolved and genetically engineered strains are examined in light of their unique attributes and responses to various biomass treatment conditions, and the genetic tools that have been employed for their creation are presented. Several future routes for potential industrial usage are presented, and it is concluded that, although there have been many advances to significantly improve C. thermocellum's amenability to industrial use, several hurdles still remain to be overcome as this unique organism enjoys increased attention within the scientific community.
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Affiliation(s)
- Hannah Akinosho
- School of Chemistry and Biochemistry, Institute of Paper Science and Technology, Georgia Institute of Technology Atlanta, GA, USA ; Oak Ridge National Laboratory, BioEnergy Science Center Oak Ridge, TN, USA
| | - Kelsey Yee
- Oak Ridge National Laboratory, BioEnergy Science Center Oak Ridge, TN, USA ; Biosciences Division, Oak Ridge National Laboratory Oak Ridge, TN, USA
| | - Dan Close
- Biosciences Division, Oak Ridge National Laboratory Oak Ridge, TN, USA
| | - Arthur Ragauskas
- Oak Ridge National Laboratory, BioEnergy Science Center Oak Ridge, TN, USA ; Department of Chemical and Biomolecular Engineering and Department of Forestry, Wildlife, and Fisheries, University of Tennessee Knoxville, TN, USA
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Role of transcription and enzyme activities in redistribution of carbon and electron flux in response to N2 and H2 sparging of open-batch cultures of Clostridium thermocellum ATCC 27405. Appl Microbiol Biotechnol 2014; 98:2829-40. [DOI: 10.1007/s00253-013-5500-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 12/18/2013] [Accepted: 12/24/2013] [Indexed: 12/17/2022]
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Thermoanaerobacter thermohydrosulfuricus WC1 shows protein complement stability during fermentation of key lignocellulose-derived substrates. Appl Environ Microbiol 2013; 80:1602-15. [PMID: 24362431 DOI: 10.1128/aem.03555-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thermoanaerobacter spp. have long been considered suitable Clostridium thermocellum coculture partners for improving lignocellulosic biofuel production through consolidated bioprocessing. However, studies using "omic"-based profiling to better understand carbon utilization and biofuel producing pathways have been limited to only a few strains thus far. To better characterize carbon and electron flux pathways in the recently isolated, xylanolytic strain, Thermoanaerobacter thermohydrosulfuricus WC1, label-free quantitative proteomic analyses were combined with metabolic profiling. SWATH-MS proteomic analysis quantified 832 proteins in each of six proteomes isolated from mid-exponential-phase cells grown on xylose, cellobiose, or a mixture of both. Despite encoding genes consistent with a carbon catabolite repression network observed in other Gram-positive organisms, simultaneous consumption of both substrates was observed. Lactate was the major end product of fermentation under all conditions despite the high expression of gene products involved with ethanol and/or acetate synthesis, suggesting that carbon flux in this strain may be controlled via metabolite-based (allosteric) regulation or is constrained by metabolic bottlenecks. Cross-species "omic" comparative analyses confirmed similar expression patterns for end-product-forming gene products across diverse Thermoanaerobacter spp. It also identified differences in cofactor metabolism, which potentially contribute to differences in end-product distribution patterns between the strains analyzed. The analyses presented here improve our understanding of T. thermohydrosulfuricus WC1 metabolism and identify important physiological limitations to be addressed in its development as a biotechnologically relevant strain in ethanologenic designer cocultures through consolidated bioprocessing.
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Wushke S, Levin DB, Cicek N, Sparling R. Characterization of enriched aerotolerant cellulose-degrading communities for biofuels production using differing selection pressures and inoculum sources. Can J Microbiol 2013; 59:679-83. [PMID: 24102221 DOI: 10.1139/cjm-2013-0430] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ethanol production from direct cellulose fermentation has mainly been described as a strictly anaerobic process. The use of air-tolerant organisms or consortia for this process would reduce the need for prereduction of the medium and also permit continuous feed of aerobic feedstock. To this end, moderately thermophilic (60 °C) consortia of fermentative, cellulolytic bacteria were enriched from 3 distinct environments (manure, marsh, and rotten wood) from a farm in southeast Saskatchewan, Canada. Community phenotypic and metabolic profiles were characterized. Selection methods included direct plating under an aerobic atmosphere and repeated passaging; the methods were designed to select for robust, stable aerotolerant cellulose-degrading communities. Several of the isolated communities exhibited an increase in total cellulose degradation and total ethanol yield when compared with a monoculture of Clostridium thermocellum DSMZ 1237. Owing to stringent selection conditions, low diversity enrichments were found, and many appeared to be binary cultures via density gradient gel electrophoresis analysis. On the basis of 16S rRNA gene sequencing, aerobic conditions selected for a mix of organisms highly related to C. thermocellum and Geobacillus species, while anaerobic conditions led to the development of consortia containing strains related to C. thermocellum with strains from either the genus Geobacillus or the genus Thermoanaerobacter. The presence of a Geobacillus-like species appeared to be a prerequisite for aerotolerance of the cellulolytic enrichments, a highly desired phenotype in lignocellulosic consolidated bioprocessing.
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Affiliation(s)
- Scott Wushke
- a Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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Xia Y, Fang HHP, Zhang T. Recent studies on thermophilic anaerobic bioconversion of lignocellulosic biomass. RSC Adv 2013. [DOI: 10.1039/c3ra40866c] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Continuous cellulosic bioethanol fermentation by cyclic fed-batch cocultivation. Appl Environ Microbiol 2012; 79:1580-9. [PMID: 23275517 DOI: 10.1128/aem.02617-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cocultivation of cellulolytic and saccharolytic microbial populations is a promising strategy to improve bioethanol production from the fermentation of recalcitrant cellulosic materials. Earlier studies have demonstrated the effectiveness of cocultivation in enhancing ethanolic fermentation of cellulose in batch fermentation. To further enhance process efficiency, a semicontinuous cyclic fed-batch fermentor configuration was evaluated for its potential in enhancing the efficiency of cellulose fermentation using cocultivation. Cocultures of cellulolytic Clostridium thermocellum LQRI and saccharolytic Thermoanaerobacter pseudethanolicus strain X514 were tested in the semicontinuous fermentor as a model system. Initial cellulose concentration and pH were identified as the key process parameters controlling cellulose fermentation performance in the fixed-volume cyclic fed-batch coculture system. At an initial cellulose concentration of 40 g liter(-1), the concentration of ethanol produced with pH control was 4.5-fold higher than that without pH control. It was also found that efficient cellulosic bioethanol production by cocultivation was sustained in the semicontinuous configuration, with bioethanol production reaching 474 mM in 96 h with an initial cellulose concentration of 80 g liter(-1) and pH controlled at 6.5 to 6.8. These results suggested the advantages of the cyclic fed-batch process for cellulosic bioethanol fermentation by the cocultures.
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Carere CR, Rydzak T, Verbeke TJ, Cicek N, Levin DB, Sparling R. Linking genome content to biofuel production yields: a meta-analysis of major catabolic pathways among select H2 and ethanol-producing bacteria. BMC Microbiol 2012; 12:295. [PMID: 23249097 PMCID: PMC3561251 DOI: 10.1186/1471-2180-12-295] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 12/12/2012] [Indexed: 12/16/2022] Open
Abstract
Background Fermentative bacteria offer the potential to convert lignocellulosic waste-streams into biofuels such as hydrogen (H2) and ethanol. Current fermentative H2 and ethanol yields, however, are below theoretical maxima, vary greatly among organisms, and depend on the extent of metabolic pathways utilized. For fermentative H2 and/or ethanol production to become practical, biofuel yields must be increased. We performed a comparative meta-analysis of (i) reported end-product yields, and (ii) genes encoding pyruvate metabolism and end-product synthesis pathways to identify suitable biomarkers for screening a microorganism’s potential of H2 and/or ethanol production, and to identify targets for metabolic engineering to improve biofuel yields. Our interest in H2 and/or ethanol optimization restricted our meta-analysis to organisms with sequenced genomes and limited branched end-product pathways. These included members of the Firmicutes, Euryarchaeota, and Thermotogae. Results Bioinformatic analysis revealed that the absence of genes encoding acetaldehyde dehydrogenase and bifunctional acetaldehyde/alcohol dehydrogenase (AdhE) in Caldicellulosiruptor, Thermococcus, Pyrococcus, and Thermotoga species coincide with high H2 yields and low ethanol production. Organisms containing genes (or activities) for both ethanol and H2 synthesis pathways (i.e. Caldanaerobacter subterraneus subsp. tengcongensis, Ethanoligenens harbinense, and Clostridium species) had relatively uniform mixed product patterns. The absence of hydrogenases in Geobacillus and Bacillus species did not confer high ethanol production, but rather high lactate production. Only Thermoanaerobacter pseudethanolicus produced relatively high ethanol and low H2 yields. This may be attributed to the presence of genes encoding proteins that promote NADH production. Lactate dehydrogenase and pyruvate:formate lyase are not conducive for ethanol and/or H2 production. While the type(s) of encoded hydrogenases appear to have little impact on H2 production in organisms that do not encode ethanol producing pathways, they do influence reduced end-product yields in those that do. Conclusions Here we show that composition of genes encoding pathways involved in pyruvate catabolism and end-product synthesis pathways can be used to approximate potential end-product distribution patterns. We have identified a number of genetic biomarkers for streamlining ethanol and H2 producing capabilities. By linking genome content, reaction thermodynamics, and end-product yields, we offer potential targets for optimization of either ethanol or H2 yields through metabolic engineering.
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Affiliation(s)
- Carlo R Carere
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada R3T 5V6
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Levin DB, Hye Jo J, Maness PC. Biohydrogen Production from Cellulosic Biomass. INTEGRATED FOREST BIOREFINERIES 2012. [DOI: 10.1039/9781849735063-00256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hydrogen can be produced by thermochemical, physicochemical, and biological processes. In contrast to thermo- and physicochemical processes, biological processes offer great potential for sustainable, renewable hydrogen production. Lignocellulosic biomass is renewable, inexpensive, constitutes a large fraction of waste biomass from municipal, agricultural, and forestry sectors, and thus offers excellent potential as a feedstock for renewable biofuels. Cellulose is, however, difficult to hydrolyze due to its crystalline structure. Biological hydrogen can be produced from cellulosic substrates by either hydrolyzing cellulose to sugars, followed by fermentation or by direct use of cellulose as the sole carbon source during fermentation. This chapter outlines the microbial basis of biological hydrogen production by cellulolytic bacteria, discusses the factors that influence hydrogen yields, and describes both single-phase and two-phase hydrogen production systems.
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Affiliation(s)
- David B Levin
- Department of Biosystems Engineering University of Manitoba Winnipeg, Manitoba, R3T 5V6 Canada
| | - Ji Hye Jo
- National Renewable Energy Laboratory 1617 Cole Blvd., Golden, Colorado, 80401 USA
| | - Pin-Ching Maness
- National Renewable Energy Laboratory 1617 Cole Blvd., Golden, Colorado, 80401 USA
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Abstract
The importance of bacterial adherence has been acknowledged in microbial lignocellulose conversion studies; however, few reports have described the function and structure of biofilms supported by cellulosic substrates. We investigated the organization, dynamic formation, and carbon flow associated with biofilms of the obligately anaerobic cellulolytic bacterium Clostridium thermocellum 27405. Using noninvasive, in situ fluorescence imaging, we showed biofilms capable of near complete substrate conversion with a characteristic monolayered cell structure without an extracellular polymeric matrix typically seen in biofilms. Cell division at the interface and terminal endospores appeared throughout all stages of biofilm growth. Using continuous-flow reactors with a rate of dilution (2 h(-1)) 12-fold higher than the bacterium's maximum growth rate, we compared biofilm activity under low (44 g/liter) and high (202 g/liter) initial cellulose loading. The average hydrolysis rate was over 3-fold higher in the latter case, while the proportions of oligomeric cellulose hydrolysis products lost from the biofilm were 13.7% and 29.1% of the total substrate carbon hydrolyzed, respectively. Fermentative catabolism was comparable between the two cellulose loadings, with ca. 4% of metabolized sugar carbon being utilized for cell production, while 75.4% and 66.7% of the two cellulose loadings, respectively, were converted to primary carbon metabolites (ethanol, acetic acid, lactic acid, carbon dioxide). However, there was a notable difference in the ethanol-to-acetic acid ratio (g/g), measured to be 0.91 for the low cellulose loading and 0.41 for the high cellulose loading. The results suggest that substrate availability for cell attachment rather than biofilm colonization rates govern the efficiency of cellulose conversion.
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Rittmann S, Herwig C. A comprehensive and quantitative review of dark fermentative biohydrogen production. Microb Cell Fact 2012; 11:115. [PMID: 22925149 PMCID: PMC3443015 DOI: 10.1186/1475-2859-11-115] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/03/2012] [Indexed: 01/25/2023] Open
Abstract
Biohydrogen production (BHP) can be achieved by direct or indirect biophotolysis, photo-fermentation and dark fermentation, whereof only the latter does not require the input of light energy. Our motivation to compile this review was to quantify and comprehensively report strains and process performance of dark fermentative BHP. This review summarizes the work done on pure and defined co-culture dark fermentative BHP since the year 1901. Qualitative growth characteristics and quantitative normalized results of H2 production for more than 2000 conditions are presented in a normalized and therefore comparable format to the scientific community.Statistically based evidence shows that thermophilic strains comprise high substrate conversion efficiency, but mesophilic strains achieve high volumetric productivity. Moreover, microbes of Thermoanaerobacterales (Family III) have to be preferred when aiming to achieve high substrate conversion efficiency in comparison to the families Clostridiaceae and Enterobacteriaceae. The limited number of results available on dark fermentative BHP from fed-batch cultivations indicates the yet underestimated potential of this bioprocessing application. A Design of Experiments strategy should be preferred for efficient bioprocess development and optimization of BHP aiming at improving medium, cultivation conditions and revealing inhibitory effects. This will enable comparing and optimizing strains and processes independent of initial conditions and scale.
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Affiliation(s)
- Simon Rittmann
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Gumpendorferstraße 1a, Vienna University of Technology, Vienna, 1060, Austria
| | - Christoph Herwig
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Gumpendorferstraße 1a, Vienna University of Technology, Vienna, 1060, Austria
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Ellis LD, Holwerda EK, Hogsett D, Rogers S, Shao X, Tschaplinski T, Thorne P, Lynd LR. Closing the carbon balance for fermentation by Clostridium thermocellum (ATCC 27405). BIORESOURCE TECHNOLOGY 2012; 103:293-9. [PMID: 22055095 DOI: 10.1016/j.biortech.2011.09.128] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 09/27/2011] [Accepted: 09/28/2011] [Indexed: 05/18/2023]
Abstract
Our lab and most others have not been able to close a carbon balance for fermentation by the thermophilic, cellulolytic anaerobe, Clostridium thermocellum. We undertook a detailed accounting of product formation in C. thermocellum ATCC 27405. Elemental analysis revealed that for both cellulose (Avicel) and cellobiose, ≥92% of the substrate carbon utilized could be accounted for in the pellet, supernatant and off-gas when including sampling. However, 11.1% of the original substrate carbon was found in the liquid phase and not in the form of commonly-measured fermentation products--ethanol, acetate, lactate, and formate. Further detailed analysis revealed all the products to be <720 da and have not usually been associated with C. thermocellum fermentation, including malate, pyruvate, uracil, soluble glucans, and extracellular free amino acids. By accounting for these products, 92.9% and 93.2% of the final product carbon was identified during growth on cellobiose and Avicel, respectively.
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Affiliation(s)
- Lucas D Ellis
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA
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Torres S, Pandey A, Castro GR. Organic solvent adaptation of Gram positive bacteria: Applications and biotechnological potentials. Biotechnol Adv 2011; 29:442-52. [DOI: 10.1016/j.biotechadv.2011.04.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Revised: 03/28/2011] [Accepted: 03/30/2011] [Indexed: 10/18/2022]
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Raman B, McKeown CK, Rodriguez M, Brown SD, Mielenz JR. Transcriptomic analysis of Clostridium thermocellum ATCC 27405 cellulose fermentation. BMC Microbiol 2011; 11:134. [PMID: 21672225 PMCID: PMC3130646 DOI: 10.1186/1471-2180-11-134] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 06/14/2011] [Indexed: 01/18/2023] Open
Abstract
Background The ability of Clostridium thermocellum ATCC 27405 wild-type strain to hydrolyze cellulose and ferment the degradation products directly to ethanol and other metabolic byproducts makes it an attractive candidate for consolidated bioprocessing of cellulosic biomass to biofuels. In this study, whole-genome microarrays were used to investigate the expression of C. thermocellum mRNA during growth on crystalline cellulose in controlled replicate batch fermentations. Results A time-series analysis of gene expression revealed changes in transcript levels of ~40% of genes (~1300 out of 3198 ORFs encoded in the genome) during transition from early-exponential to late-stationary phase. K-means clustering of genes with statistically significant changes in transcript levels identified six distinct clusters of temporal expression. Broadly, genes involved in energy production, translation, glycolysis and amino acid, nucleotide and coenzyme metabolism displayed a decreasing trend in gene expression as cells entered stationary phase. In comparison, genes involved in cell structure and motility, chemotaxis, signal transduction and transcription showed an increasing trend in gene expression. Hierarchical clustering of cellulosome-related genes highlighted temporal changes in composition of this multi-enzyme complex during batch growth on crystalline cellulose, with increased expression of several genes encoding hydrolytic enzymes involved in degradation of non-cellulosic substrates in stationary phase. Conclusions Overall, the results suggest that under low substrate availability, growth slows due to decreased metabolic potential and C. thermocellum alters its gene expression to (i) modulate the composition of cellulosomes that are released into the environment with an increased proportion of enzymes than can efficiently degrade plant polysaccharides other than cellulose, (ii) enhance signal transduction and chemotaxis mechanisms perhaps to sense the oligosaccharide hydrolysis products, and nutrient gradients generated through the action of cell-free cellulosomes and, (iii) increase cellular motility for potentially orienting the cells' movement towards positive environmental signals leading to nutrient sources. Such a coordinated cellular strategy would increase its chances of survival in natural ecosystems where feast and famine conditions are frequently encountered.
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Affiliation(s)
- Babu Raman
- Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831, USA
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RenNanqi, GuoWanqian, LiuBingfeng, CaoGuangli, DingJie. Biological hydrogen production by dark fermentation: challenges and prospects towards scaled-up production. Curr Opin Biotechnol 2011; 22:365-70. [PMID: 21612910 DOI: 10.1016/j.copbio.2011.04.022] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 04/23/2011] [Accepted: 04/27/2011] [Indexed: 11/30/2022]
Abstract
Among different technologies of hydrogen production, bio-hydrogen production exhibits perhaps the greatest potential to replace fossil fuels. Based on recent research on dark fermentative hydrogen production, this article reviews the following aspects towards scaled-up application of this technology: bioreactor development and parameter optimization, process modeling and simulation, exploitation of cheaper raw materials and combining dark-fermentation with photo-fermentation. Bioreactors are necessary for dark-fermentation hydrogen production, so the design of reactor type and optimization of parameters are essential. Process modeling and simulation can help engineers design and optimize large-scale systems and operations. Use of cheaper raw materials will surely accelerate the pace of scaled-up production of biological hydrogen. And finally, combining dark-fermentation with photo-fermentation holds considerable promise, and has successfully achieved maximum overall hydrogen yield from a single substrate. Future development of bio-hydrogen production will also be discussed.
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Affiliation(s)
- RenNanqi
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, PR China.
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Jeon E, Hyeon JE, Suh DJ, Suh YW, Kim SW, Song KH, Han SO. Production of cellulosic ethanol in Saccharomyces cerevisiae heterologous expressing Clostridium thermocellum endoglucanase and Saccharomycopsis fibuligera beta-glucosidase genes. Mol Cells 2009; 28:369-73. [PMID: 19812901 DOI: 10.1007/s10059-009-0131-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 07/23/2009] [Accepted: 08/17/2009] [Indexed: 10/20/2022] Open
Abstract
Heterologous secretory expression of endoglucanase E (Clostridium thermocellum) and beta-glucosidase 1 (Saccharomycopsis fibuligera) was achieved in Saccharomyces cerevisiae fermentation cultures as an alpha-mating factor signal peptide fusion, based on the native enzyme coding sequence. Ethanol production depends on simultaneous saccharification of cellulose to glucose and fermentation of glucose to ethanol by a recombinant yeast strain as a microbial biocatalyst. Recombinant yeast strain expressing endoglucanase and beta-glucosidase was able to produce ethanol from beta-glucan, CMC and acid swollen cellulose. This indicates that the resultant yeast strain of this study acts efficiently as a whole cell biocatalyst.
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Affiliation(s)
- Eugene Jeon
- School of Life Science and Biotechnology, Korea University, Seoul 136-701, Korea
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