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Tunca B, Kutlar FE, Kas A, Yilmazel YD. Enhanced biohydrogen production from high loads of unpretreated cattle manure by cellulolytic bacterium Caldicellulosiruptor bescii at 75 °C. WASTE MANAGEMENT (NEW YORK, N.Y.) 2023; 171:401-410. [PMID: 37776811 DOI: 10.1016/j.wasman.2023.09.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 09/12/2023] [Accepted: 09/21/2023] [Indexed: 10/02/2023]
Abstract
Caldicellulosiruptor bescii is the most thermophilic cellulolytic bacterium capable of fermenting crystalline cellulose identified to date, and it also has a superior ability to degrade plant biomass without any pretreatment. This study is the first to assess the potential of utilizing unpretreated cattle manure (UCM) as a feedstock for hydrogen (H2) production by C. bescii at a concentration range between 2.5-50 g volatile solids (VS)/L. At 50 g VS/L UCM concentrations, H2 production ceased due to inhibition of C. bescii. To alleviate the impacts of inhibition, two strategies were adopted: (i) reduction of H2 build-up in the reactor headspace via gas sparging and (ii) adaptation of C. bescii to UCM via adaptive laboratory evolution (ALE). The former increased H2 yield by 47% compared to the control reactors, where no sparging was applied. The latter increased H2 yield by 142% compared to the control reactors inoculated by the wild type C. bescii. The UCM-adapted C. bescii demonstrated a remarkable H2 yield of 161.3 ± 1.6 mL H2/g VSadded at 15 g VS/L. This yield represents a twofold increase compared to the maximum H2 yield reported in the literature amongst fermentation studies utilizing manure as feed. At 15 g VS/L, around 73% of UCM was solubilized, and the carbon balance indicated that most of the effluent carbon was in the sugar- and acid-form. The remarkable ability of C. bescii to produce H2 from UCM under non-sterile conditions presents a significant potential for sustainable biohydrogen production from renewable feedstocks.
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Affiliation(s)
- Berivan Tunca
- Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey
| | - Feride Ece Kutlar
- Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey
| | - Aykut Kas
- Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey
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Thermophilic Water Gas Shift Reaction at High Carbon Monoxide and Hydrogen Partial Pressures in Parageobacillus thermoglucosidasius KP1013. FERMENTATION 2022. [DOI: 10.3390/fermentation8110596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The facultatively anaerobic Parageobacillus thermoglucosidasius oxidizes carbon monoxide to produce hydrogen via the water gas shift (WGS) reaction. In the current work, we examined the influence of carbon monoxide (CO) and hydrogen (H2) on the WGS reaction in the thermophilic P. thermoglucosidasius by cultivating two hydrogenogenic strains under varying CO and H2 compositions. Microbial growth and dynamics of the WGS reaction were monitored by evaluating parameters such as pressure, headspace composition, metabolic intermediates, pH, and optical density. Our analyses revealed that compared to the previously studied P. thermoglucosidasius strains, the strain KP1013 demonstrated higher CO tolerance and improved WGS reaction kinetics. Under anaerobic conditions, the lag phase before the WGS reaction shortened to 8 h, with KP1013 showing no hydrogen-induced product inhibition at hydrogen partial pressures up to 1.25 bar. The observed lack of product inhibition and the reduced lag phase of the WGS reaction support the possibility of establishing an industrial process for biohydrogen production with P. thermoglucosidasius.
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Byrne E, Björkmalm J, Bostick JP, Sreenivas K, Willquist K, van Niel EWJ. Characterization and adaptation of Caldicellulosiruptor strains to higher sugar concentrations, targeting enhanced hydrogen production from lignocellulosic hydrolysates. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:210. [PMID: 34717729 PMCID: PMC8557575 DOI: 10.1186/s13068-021-02058-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 10/17/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND The members of the genus Caldicellulosiruptor have the potential for future integration into a biorefinery system due to their capacity to generate hydrogen close to the theoretical limit of 4 mol H2/mol hexose, use a wide range of sugars and can grow on numerous lignocellulose hydrolysates. However, members of this genus are unable to survive in high sugar concentrations, limiting their ability to grow on more concentrated hydrolysates, thus impeding their industrial applicability. In this study five members of this genus, C. owensensis, C. kronotskyensis, C. bescii, C. acetigenus and C. kristjanssonii, were developed to tolerate higher sugar concentrations through an adaptive laboratory evolution (ALE) process. The developed mixed population C. owensensis CO80 was further studied and accompanied by the development of a kinetic model based on Monod kinetics to quantitatively compare it with the parental strain. RESULTS Mixed populations of Caldicellulosiruptor tolerant to higher glucose concentrations were obtained with C. owensensis adapted to grow up to 80 g/L glucose; other strains in particular C. kristjanssonii demonstrated a greater restriction to adaptation. The C. owensensis CO80 mixed population was further studied and demonstrated the ability to grow in glucose concentrations up to 80 g/L glucose, but with reduced volumetric hydrogen productivities ([Formula: see text]) and incomplete sugar conversion at elevated glucose concentrations. In addition, the carbon yield decreased with elevated concentrations of glucose. The ability of the mixed population C. owensensis CO80 to grow in high glucose concentrations was further described with a kinetic growth model, which revealed that the critical sugar concentration of the cells increased fourfold when cultivated at higher concentrations. When co-cultured with the adapted C. saccharolyticus G5 mixed culture at a hydraulic retention time (HRT) of 20 h, C. owensensis constituted only 0.09-1.58% of the population in suspension. CONCLUSIONS The adaptation of members of the Caldicellulosiruptor genus to higher sugar concentrations established that the ability to develop improved strains via ALE is species dependent, with C. owensensis adapted to grow on 80 g/L, whereas C. kristjanssonii could only be adapted to 30 g/L glucose. Although C. owensensis CO80 was adapted to a higher sugar concentration, this mixed population demonstrated reduced [Formula: see text] with elevated glucose concentrations. This would indicate that while ALE permits adaptation to elevated sugar concentrations, this approach does not result in improved fermentation performances at these higher sugar concentrations. Moreover, the observation that planktonic mixed culture of CO80 was outcompeted by an adapted C. saccharolyticus, when co-cultivated in continuous mode, indicates that the robustness of CO80 mixed culture should be improved for industrial application.
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Affiliation(s)
- Eoin Byrne
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
- Department of Food Biosciences, Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, P61 C996, Ireland
| | - Johanna Björkmalm
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
- RISE, Ideon Science Park, Building Beta 2 3v Scheelevägen 17, 22370, Lund, Sweden
| | - James P Bostick
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
- Coriolis Pharma Research GmbH, Fraunhoferstrasse 18B, 82152, Planegg, Germany
| | - Krishnan Sreenivas
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
| | - Karin Willquist
- RISE, Ideon Science Park, Building Beta 2 3v Scheelevägen 17, 22370, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden.
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Vongkampang T, Sreenivas K, Engvall J, Grey C, van Niel EWJ. Characterization of simultaneous uptake of xylose and glucose in Caldicellulosiruptor kronotskyensis for optimal hydrogen production. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:91. [PMID: 33832529 PMCID: PMC8034154 DOI: 10.1186/s13068-021-01938-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 03/22/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Caldicellulosiruptor kronotskyensis has gained interest for its ability to grow on various lignocellulosic biomass. The aim of this study was to investigate the growth profiles of C. kronotskyensis in the presence of mixtures of glucose-xylose. Recently, we characterized a diauxic-like pattern for C. saccharolyticus on lignocellulosic sugar mixtures. In this study, we aimed to investigate further whether C. kronotskyensis has adapted to uptake glucose in the disaccharide form (cellobiose) rather than the monosaccharide (glucose). RESULTS Interestingly, growth of C. kronotskyensis on glucose and xylose mixtures did not display diauxic-like growth patterns. Closer investigation revealed that, in contrast to C. saccharolyticus, C. kronotskyensis does not possess a second uptake system for glucose. Both C. saccharolyticus and C. kronotskyensis share the characteristics of preferring xylose over glucose. Growth on xylose was twice as fast (μmax = 0.57 h-1) as on glucose (μmax = 0.28 h-1). A study of the sugar uptake was made with different glucose-xylose ratios to find a kinetic relationship between the two sugars for transport into the cell. High concentrations of glucose inhibited xylose uptake and vice versa. The inhibition constants were estimated to be KI,glu = 0.01 cmol L-1 and KI,xyl = 0.001 cmol L-1, hence glucose uptake was more severely inhibited by xylose uptake. Bioinformatics analysis could not exclude that C. kronotskyensis possesses more than one transporter for glucose. As a next step it was investigated whether glucose uptake by C. kronotskyensis improved in the form of cellobiose. Indeed, cellobiose is taken up faster than glucose; nevertheless, the growth rate on each sugar remained similar. CONCLUSIONS C. kronotskyensis possesses a xylose transporter that might take up glucose at an inferior rate even in the absence of xylose. Alternatively, glucose can be taken up in the form of cellobiose, but growth performance is still inferior to growth on xylose. Therefore, we propose that the catabolism of C. kronotskyensis has adapted more strongly to pentose rather than hexose, thereby having obtained a specific survival edge in thermophilic lignocellulosic degradation communities.
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Affiliation(s)
- Thitiwut Vongkampang
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden.
| | - Krishnan Sreenivas
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
| | - Jonathan Engvall
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
| | - Carl Grey
- Division of Biotechnology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
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Usai G, Cirrincione S, Re A, Manfredi M, Pagnani A, Pessione E, Mazzoli R. Clostridium cellulovorans metabolism of cellulose as studied by comparative proteomic approach. J Proteomics 2020; 216:103667. [DOI: 10.1016/j.jprot.2020.103667] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/31/2019] [Accepted: 01/22/2020] [Indexed: 12/15/2022]
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Sander KB, Chung D, Klingeman DM, Giannone RJ, Rodriguez M, Whitham J, Hettich RL, Davison BH, Westpheling J, Brown SD. Gene targets for engineering osmotolerance in Caldicellulosiruptor bescii. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:50. [PMID: 32190115 PMCID: PMC7071700 DOI: 10.1186/s13068-020-01690-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 02/27/2020] [Indexed: 05/05/2023]
Abstract
BACKGROUND Caldicellulosiruptor bescii, a promising biocatalyst being developed for use in consolidated bioprocessing of lignocellulosic materials to ethanol, grows poorly and has reduced conversion at elevated medium osmolarities. Increasing tolerance to elevated fermentation osmolarities is desired to enable performance necessary of a consolidated bioprocessing (CBP) biocatalyst. RESULTS Two strains of C. bescii showing growth phenotypes in elevated osmolarity conditions were identified. The first strain, ORCB001, carried a deletion of the FapR fatty acid biosynthesis and malonyl-CoA metabolism repressor and had a severe growth defect when grown in high-osmolarity conditions-introduced as the addition of either ethanol, NaCl, glycerol, or glucose to growth media. The second strain, ORCB002, displayed a growth rate over three times higher than its genetic parent when grown in high-osmolarity medium. Unexpectedly, a genetic complement ORCB002 exhibited improved growth, failing to revert the observed phenotype, and suggesting that mutations other than the deleted transcription factor (the fruR/cra gene) are responsible for the growth phenotype observed in ORCB002. Genome resequencing identified several other genomic alterations (three deleted regions, three substitution mutations, one silent mutation, and one frameshift mutation), which may be responsible for the observed increase in osmolarity tolerance in the fruR/cra-deficient strain, including a substitution mutation in dnaK, a gene previously implicated in osmoresistance in bacteria. Differential expression analysis and transcription factor binding site inference indicates that FapR negatively regulates malonyl-CoA and fatty acid biosynthesis, as it does in many other bacteria. FruR/Cra regulates neighboring fructose metabolism genes, as well as other genes in global manner. CONCLUSIONS Two systems able to effect tolerance to elevated osmolarities in C. bescii are identified. The first is fatty acid biosynthesis. The other is likely the result of one or more unintended, secondary mutations present in another transcription factor deletion strain. Though the locus/loci and mechanism(s) responsible remain unknown, candidate mutations are identified, including a mutation in the dnaK chaperone coding sequence. These results illustrate both the promise of targeted regulatory manipulation for osmotolerance (in the case of fapR) and the challenges (in the case of fruR/cra).
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Affiliation(s)
- Kyle B. Sander
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Bredesen Center for Interdisciplinary Graduate Research and Education, University of Tennessee, Knoxville, TN USA
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN USA
- Present Address: Department of Bioengineering, University of California, Berkeley, Berkeley, CA USA
| | - Daehwan Chung
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Department of Genetics, University of Georgia, Athens, GA USA
- Present Address: National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Dawn M. Klingeman
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Richard J. Giannone
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Miguel Rodriguez
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Jason Whitham
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Present Address: Becton Dickinson Diagnostics, Sparks Glencoe, MD USA
| | - Robert L. Hettich
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Brian H. Davison
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Bredesen Center for Interdisciplinary Graduate Research and Education, University of Tennessee, Knoxville, TN USA
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Janet Westpheling
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Department of Genetics, University of Georgia, Athens, GA USA
| | - Steven D. Brown
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Bredesen Center for Interdisciplinary Graduate Research and Education, University of Tennessee, Knoxville, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Present Address: LanzaTech, Skokie, IL USA
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Dreschke G, Papirio S, Scala A, Lens PNL, Esposito G. High rate continuous biohydrogen production by hyperthermophilic Thermotoga neapolitana. BIORESOURCE TECHNOLOGY 2019; 293:122033. [PMID: 31472408 DOI: 10.1016/j.biortech.2019.122033] [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: 07/17/2019] [Revised: 08/15/2019] [Accepted: 08/16/2019] [Indexed: 06/10/2023]
Abstract
This study focused on continuous-flow hydrogen production by Thermotoga neapolitana at a hydraulic retention time (HRT) decreasing from 24 to 5 h. At each HRT reduction, the hydrogen yield (HY) immediately dropped, but recovered during prolonged cultivation at constant HRT. The final HY in each operating period decreased from 3.4 (±0.1) to 2.0 (±0.0) mol H2/mol glucose when reducing the HRT from 24 to 7 h. Simultaneously, the hydrogen production rate (HPR) and the liquid phase hydrogen concentration (H2aq) increased from 82 (±1) to 192 (±4) mL/L/h and from 9.1 (±0.3) to 15.6 (±0.7) mL/L, respectively. Additionally, the effluent glucose concentration increased from 2.1 (±0.1) to above 10 mM. Recirculating H2-rich biogas prevented the supersaturation of H2aq reaching a value of 9.3 (±0.7) mL/L, resulting in complete glucose consumption and the highest HPR of 277 mL/L/h at an HRT of 5 h.
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Affiliation(s)
- Gilbert Dreschke
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Via Di Biasio, 43, 03043 Cassino, FR, Italy.
| | - Stefano Papirio
- Department of Civil, Architectural and Environmental Engineering, University of Napoli Federico II, Via Claudio 21, 80125 Napoli, Italy
| | - Alessio Scala
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Via Di Biasio, 43, 03043 Cassino, FR, Italy
| | - Piet N L Lens
- UNESCO - IHE Institute for Water Education, Westvest 7, 2611-AX Delft, The Netherlands
| | - Giovanni Esposito
- Department of Civil, Architectural and Environmental Engineering, University of Napoli Federico II, Via Claudio 21, 80125 Napoli, Italy
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Li L, Li Y, Yasser Farouk R, Wang Y. Three-ways changed in headspace air on anaerobic fermentation. BIORESOURCE TECHNOLOGY 2019; 289:121684. [PMID: 31247528 DOI: 10.1016/j.biortech.2019.121684] [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: 05/28/2019] [Revised: 06/16/2019] [Accepted: 06/18/2019] [Indexed: 06/09/2023]
Abstract
Different headspace condition has a great influence on fermentation process. In this study, whey protein was used as substrate, and the headspace air was changed in three different ways (H2 mixed N2, H2 mixed CO2, N2 with different sparging rates) to explore the effects of these three methods on products. The result showed that H2 mixed with CO2 is more conducive to acid production. Homoacetogenesis played a central role in fermentation process. There is a turning point in the role of hydrogen and Homoacetogenesis, which is when the partial pressure of hydrogen is 0.268 atm. In the first two conditions, the acid concentration increased with the increase of hydrogen percentage. Nitrogen sparging way is adverse to acid production, but conducive to gas production.
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Affiliation(s)
- Leigang Li
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Yu Li
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Reham Yasser Farouk
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, PR China; Department of Agricultural Engineering, Faculty of Agriculture, Cairo University, 12613 Giza, Egypt
| | - Yuanyuan Wang
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, PR China.
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Björkmalm J, Byrne E, van Niel EWJ, Willquist K. A non-linear model of hydrogen production by Caldicellulosiruptor saccharolyticus for diauxic-like consumption of lignocellulosic sugar mixtures. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:175. [PMID: 29977336 PMCID: PMC6013967 DOI: 10.1186/s13068-018-1171-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 06/12/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Caldicellulosiruptor saccharolyticus is an attractive hydrogen producer suitable for growth on various lignocellulosic substrates. The aim of this study was to quantify uptake of pentose and hexose monosaccharides in an industrial substrate and to present a kinetic growth model of C. saccharolyticus that includes sugar uptake on defined and industrial media. The model is based on Monod and Hill kinetics extended with gas-to-liquid mass transfer and a cybernetic approach to describe diauxic-like growth. RESULTS Mathematical expressions were developed to describe hydrogen production by C. saccharolyticus consuming glucose, xylose, and arabinose. The model parameters were calibrated against batch fermentation data. The experimental data included four different cases: glucose, xylose, sugar mixture, and wheat straw hydrolysate (WSH) fermentations. The fermentations were performed without yeast extract. The substrate uptake rate of C. saccharolyticus on single sugar-defined media was higher on glucose compared to xylose. In contrast, in the defined sugar mixture and WSH, the pentoses were consumed faster than glucose. Subsequently, the cultures entered a lag phase when all pentoses were consumed after which glucose uptake rate increased. This phenomenon suggested a diauxic-like behavior as was deduced from the successive appearance of two peaks in the hydrogen and carbon dioxide productivity. The observation could be described with a modified diauxic model including a second enzyme system with a higher affinity for glucose being expressed when pentose saccharides are consumed. This behavior was more pronounced when WSH was used as substrate. CONCLUSIONS The previously observed co-consumption of glucose and pentoses with a preference for the latter was herein confirmed. However, once all pentoses were consumed, C. saccharolyticus most probably expressed another uptake system to account for the observed increased glucose uptake rate. This phenomenon could be quantitatively captured in a kinetic model of the entire diauxic-like growth process. Moreover, the observation indicates a regulation system that has fundamental research relevance, since pentose and glucose uptake in C. saccharolyticus has only been described with ABC transporters, whereas previously reported diauxic growth phenomena have been correlated mainly to PTS systems for sugar uptake.
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Affiliation(s)
- Johanna Björkmalm
- Department of Energy and Circular Economy, RISE Research Institutes of Sweden, PO Box 857, 501 15 Borås, Sweden
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Eoin Byrne
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Karin Willquist
- Department of Energy and Circular Economy, RISE Research Institutes of Sweden, PO Box 857, 501 15 Borås, Sweden
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Gannoun H, Gaida LB, Saidi R, Miladi B, Hamdi M, Bouallagui H, Liebgott PP, Auria R. A simple gas pressure manometer for measuring hydrogen production by hydrogenogenic cultures in serum bottles. Process Biochem 2018. [DOI: 10.1016/j.procbio.2017.10.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Counts JA, Zeldes BM, Lee LL, Straub CT, Adams MWW, Kelly RM. Physiological, metabolic and biotechnological features of extremely thermophilic microorganisms. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2017; 9. [PMID: 28206708 DOI: 10.1002/wsbm.1377] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 11/23/2016] [Accepted: 11/30/2016] [Indexed: 12/12/2022]
Abstract
The current upper thermal limit for life as we know it is approximately 120°C. Microorganisms that grow optimally at temperatures of 75°C and above are usually referred to as 'extreme thermophiles' and include both bacteria and archaea. For over a century, there has been great scientific curiosity in the basic tenets that support life in thermal biotopes on earth and potentially on other solar bodies. Extreme thermophiles can be aerobes, anaerobes, autotrophs, heterotrophs, or chemolithotrophs, and are found in diverse environments including shallow marine fissures, deep sea hydrothermal vents, terrestrial hot springs-basically, anywhere there is hot water. Initial efforts to study extreme thermophiles faced challenges with their isolation from difficult to access locales, problems with their cultivation in laboratories, and lack of molecular tools. Fortunately, because of their relatively small genomes, many extreme thermophiles were among the first organisms to be sequenced, thereby opening up the application of systems biology-based methods to probe their unique physiological, metabolic and biotechnological features. The bacterial genera Caldicellulosiruptor, Thermotoga and Thermus, and the archaea belonging to the orders Thermococcales and Sulfolobales, are among the most studied extreme thermophiles to date. The recent emergence of genetic tools for many of these organisms provides the opportunity to move beyond basic discovery and manipulation to biotechnologically relevant applications of metabolic engineering. WIREs Syst Biol Med 2017, 9:e1377. doi: 10.1002/wsbm.1377 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- James A Counts
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Benjamin M Zeldes
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Laura L Lee
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Christopher T Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
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Auria R, Boileau C, Davidson S, Casalot L, Christen P, Liebgott PP, Combet-Blanc Y. Hydrogen production by the hyperthermophilic bacterium Thermotoga maritima Part II: modeling and experimental approaches for hydrogen production. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:268. [PMID: 28018485 PMCID: PMC5168804 DOI: 10.1186/s13068-016-0681-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/02/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. RESULTS Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2-0.5 g/L, or 0.01-0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model validity, predictions of the model show that the combination of both variables (increase in limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H2-specific productivity with the lowest inhibition. CONCLUSIONS A mathematical model predicting H2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the limit of validity of such mathematical models. Their limit of applicability must take into account the range of validity in which the parameters were established.
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Affiliation(s)
- Richard Auria
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
| | - Céline Boileau
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
| | - Sylvain Davidson
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
| | - Laurence Casalot
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
| | - Pierre Christen
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
| | - Pierre Pol Liebgott
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
| | - Yannick Combet-Blanc
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, Mediterranean Institute of Oceanography, 13288 Marseille, France
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van Niel EWJ. Biological Processes for Hydrogen Production. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2016; 156:155-193. [PMID: 27277394 DOI: 10.1007/10_2016_11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Methane is produced usually from organic waste in a straightforward anaerobic digestion process. However, hydrogen production is technically more challenging as more stages are needed to convert all biomass to hydrogen because of thermodynamic constraints. Nevertheless, the benefit of hydrogen is that it can be produced, both biologically and thermochemically, in more than one way from either organic compounds or water. Research in biological hydrogen production is booming, as reflected by the myriad of recently published reviews on the topic. This overview is written from the perspective of how to transfer as much energy as possible from the feedstock into the gaseous products hydrogen, and to a lesser extent, methane. The status and remaining challenges of all the biological processes are concisely discussed.
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Affiliation(s)
- Ed W J van Niel
- Division of Applied Microbiology, Lund University, 124, 221 00, Lund, Sweden.
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Ciranna A, Pawar SS, Santala V, Karp M, van Niel EWJ. Assessment of metabolic flux distribution in the thermophilic hydrogen producer Caloramator celer as affected by external pH and hydrogen partial pressure. Microb Cell Fact 2014; 13:48. [PMID: 24678972 PMCID: PMC3986597 DOI: 10.1186/1475-2859-13-48] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 03/18/2014] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Caloramator celer is a strict anaerobic, alkalitolerant, thermophilic bacterium capable of converting glucose to hydrogen (H2), carbon dioxide, acetate, ethanol and formate by a mixed acid fermentation. Depending on the growth conditions C. celer can produce H2 at high yields. For a biotechnological exploitation of this bacterium for H2 production it is crucial to understand the factors that regulate carbon and electron fluxes and therefore the final distribution of metabolites to channel the metabolic flux towards the desired product. RESULTS Combining experimental results from batch fermentations with genome analysis, reconstruction of central carbon metabolism and metabolic flux analysis (MFA), this study shed light on glucose catabolism of the thermophilic alkalitolerant bacterium C. celer. Two innate factors pertaining to culture conditions have been identified to significantly affect the metabolic flux distribution: culture pH and partial pressures of H2 (PH2). Overall, at alkaline to neutral pH the rate of biomass synthesis was maximized, whereas at acidic pH the lower growth rate and the less efficient biomass formation are accompanied with more efficient energy recovery from the substrate indicating high cell maintenance possibly to sustain intracellular pH homeostasis. Higher H2 yields were associated with fermentation at acidic pH as a consequence of the lower synthesis of other reduced by-products such as formate and ethanol. In contrast, PH2 did not affect the growth of C. celer on glucose. At high PH2 the cellular redox state was balanced by rerouting the flow of carbon and electrons to ethanol and formate production allowing unaltered glycolytic flux and growth rate, but resulting in a decreased H2 synthesis. CONCLUSION C. celer possesses a flexible fermentative metabolism that allows redistribution of fluxes at key metabolic nodes to simultaneously control redox state and efficiently harvest energy from substrate even under unfavorable conditions (i.e. low pH and high PH2). With the H2 production in mind, acidic pH and low PH2 should be preferred for a high yield-oriented process, while a high productivity-oriented process can be achieved at alkaline pH and high PH2.
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Affiliation(s)
- Alessandro Ciranna
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, FI-33720 Tampere, Finland
| | - Sudhanshu S Pawar
- Department of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Ville Santala
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, FI-33720 Tampere, Finland
| | - Matti Karp
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, FI-33720 Tampere, Finland
| | - Ed WJ van Niel
- Department of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
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Cai J, Wang G. Photo-biological hydrogen production by an acid tolerant mutant of Rhodovulum sulfidophilum P5 generated by transposon mutagenesis. BIORESOURCE TECHNOLOGY 2014; 154:254-259. [PMID: 24412477 DOI: 10.1016/j.biortech.2013.12.057] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 12/10/2013] [Accepted: 12/12/2013] [Indexed: 06/03/2023]
Abstract
Most of the photosynthetic bacterial strains exhibit optimum hydrogen production at neutral initial pH, and lower initial pH resulted in a sharp decrease in hydrogen yield. Thus, screening of acid-tolerant hydrogen-producing photosynthetic bacteria is very important. To obtain acid tolerant mutants, a Tn7-based transposon was randomly inserted into the genomic DNA of Rhodovulum sulfidophilum P5. An acid tolerant mutant strain TH-102 exhibited increased hydrogen production in acidic environment (pH 4.5-6.5) and at higher temperatures (35 and 37°C) than the wild-type strain. At pH 5.5 and 35°C, the mutant strain TH-102 continuously produced hydrogen. The hydrogen yield and average rate were 2.16 ± 0.10 mol/mol acetate and 10.06 ± 0.47 mL/Lh, which was about 17.32 and 15.37-fold higher than that of the wild-type strain, respectively. This acid- and temperature-tolerant mutant strain TH-102 could be used in a cost-effective hydrogen production process employing both dark fermentative and photosynthetic bacteria.
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Affiliation(s)
- Jinling Cai
- Tianjin Key Laboratory of Marine Resources and Chemistry, College of Marine Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, PR China.
| | - Guangce Wang
- Tianjin Key Laboratory of Marine Resources and Chemistry, College of Marine Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, PR China; Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, Shandong, PR China.
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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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Linville JL, Rodriguez M, Mielenz JR, Cox CD. Kinetic modeling of batch fermentation for Populus hydrolysate tolerant mutant and wild type strains of Clostridium thermocellum. BIORESOURCE TECHNOLOGY 2013; 147:605-613. [PMID: 24036527 DOI: 10.1016/j.biortech.2013.08.086] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 08/12/2013] [Accepted: 08/13/2013] [Indexed: 05/04/2023]
Abstract
The extent of inhibition of two strains of Clostridium thermocellum by a Populus hydrolysate was investigated. A Monod-based model of wild type (WT) and Populus hydrolysate tolerant mutant (PM) strains of the cellulolytic bacterium C. thermocellum was developed to quantify growth kinetics in standard media and the extent of inhibition to a Populus hydrolysate. The PM was characterized by a higher growth rate (μmax=1.223 vs. 0.571 h(-1)) and less inhibition (KI,gen=0.991 vs. 0.757) in 10% v/v Populus hydrolysate compared to the WT. In 17.5% v/v Populus hydrolysate inhibition of PM increased slightly (KI,gen=0.888), whereas the WT was strongly inhibited and did not grow in a reproducible manner. Of the individual inhibitors tested, 4-hydroxybenzoic acid was the most inhibitory, followed by galacturonic acid. The PM did not have a greater ability to detoxify the hydrolysate than the WT.
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Affiliation(s)
- Jessica L Linville
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, United States; Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Miguel Rodriguez
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, United States; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Jonathan R Mielenz
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, United States; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Chris D Cox
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, United States; Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, United States; Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, United States.
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Pawar SS, van Niel EWJ. Thermophilic biohydrogen production: how far are we? Appl Microbiol Biotechnol 2013; 97:7999-8009. [PMID: 23948723 PMCID: PMC3757257 DOI: 10.1007/s00253-013-5141-1] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 07/16/2013] [Accepted: 07/17/2013] [Indexed: 01/10/2023]
Abstract
Apart from being applied as an energy carrier, hydrogen is in increasing demand as a commodity. Currently, the majority of hydrogen (H2) is produced from fossil fuels, but from an environmental perspective, sustainable H2 production should be considered. One of the possible ways of hydrogen production is through fermentation, in particular, at elevated temperature, i.e. thermophilic biohydrogen production. This short review recapitulates the current status in thermophilic biohydrogen production through fermentation of commercially viable substrates produced from readily available renewable resources, such as agricultural residues. The route to commercially viable biohydrogen production is a multidisciplinary enterprise. Microbiological studies have pointed out certain desirable physiological characteristics in H2-producing microorganisms. More process-oriented research has identified best applicable reactor types and cultivation conditions. Techno-economic and life cycle analyses have identified key process bottlenecks with respect to economic feasibility and its environmental impact. The review has further identified current limitations and gaps in the knowledge, and also deliberates directions for future research and development of thermophilic biohydrogen production.
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Affiliation(s)
- Sudhanshu S Pawar
- Applied Microbiology, Lund University, Getingevägen 60, 222 41, Lund, Sweden.
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Talluri S, Raj SM, Christopher LP. Consolidated bioprocessing of untreated switchgrass to hydrogen by the extreme thermophile Caldicellulosiruptor saccharolyticus DSM 8903. BIORESOURCE TECHNOLOGY 2013; 139:272-9. [PMID: 23665687 DOI: 10.1016/j.biortech.2013.04.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 04/01/2013] [Accepted: 04/02/2013] [Indexed: 05/10/2023]
Abstract
The abilities of the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus DSM 8903 to ferment switchgrass (SWG), microcrystalline cellulose (MCC) and glucose to hydrogen (H2) in one-step were examined. Hydrogen production from glucose reached the theoretical maximum for dark fermentation of 4 mol H2/mol glucose. The H2 yield on MCC and SWG after 6 days of fermentation was 23.2 mmol H2/L or 9.4 mmol H2/g MCC and 14.3 mmol H2/L or 11.2 mmol H2/g SWG, respectively. The rate of H2 formation however was higher on MCC (0.7 mmol/Lh) than SWG (0.1 mmol/Lh). C. saccharolyticus DSM 8903 was able to produce H2 directly from mechanically-comminuted SWG without any physicochemical or biological pretreatment. Combining four processing steps (pretreatment, enzyme production, saccharification and fermentation) into a single biorefinery operation makes C. saccharolyticus DSM 8903 a promising candidate for consolidated bioprocessing (CBP) of lignocellulosic biomass.
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Affiliation(s)
- Suvarna Talluri
- Center for Bioprocessing Research and Development, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
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Biohydrogen Production by the Thermophilic Bacterium Caldicellulosiruptor saccharolyticus: Current Status and Perspectives. Life (Basel) 2013; 3:52-85. [PMID: 25371332 PMCID: PMC4187192 DOI: 10.3390/life3010052] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 01/06/2013] [Accepted: 01/07/2013] [Indexed: 01/24/2023] Open
Abstract
Caldicellulosiruptor saccharolyticus is one of the most thermophilic cellulolytic organisms known to date. This Gram-positive anaerobic bacterium ferments a broad spectrum of mono-, di- and polysaccharides to mainly acetate, CO2 and hydrogen. With hydrogen yields approaching the theoretical limit for dark fermentation of 4 mol hydrogen per mol hexose, this organism has proven itself to be an excellent candidate for biological hydrogen production. This review provides an overview of the research on C. saccharolyticus with respect to the hydrolytic capability, sugar metabolism, hydrogen formation, mechanisms involved in hydrogen inhibition, and the regulation of the redox and carbon metabolism. Analysis of currently available fermentation data reveal decreased hydrogen yields under non-ideal cultivation conditions, which are mainly associated with the accumulation of hydrogen in the liquid phase. Thermodynamic considerations concerning the reactions involved in hydrogen formation are discussed with respect to the dissolved hydrogen concentration. Novel cultivation data demonstrate the sensitivity of C. saccharolyticus to increased hydrogen levels regarding substrate load and nitrogen limitation. In addition, special attention is given to the rhamnose metabolism, which represents an unusual type of redox balancing. Finally, several approaches are suggested to improve biohydrogen production by C. saccharolyticus.
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Improved growth media and culture techniques for genetic analysis and assessment of biomass utilization by Caldicellulosiruptor bescii. J Ind Microbiol Biotechnol 2012; 40:41-9. [PMID: 23149625 DOI: 10.1007/s10295-012-1202-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 09/19/2012] [Indexed: 11/27/2022]
Abstract
Methods for efficient growth and manipulation of relatively uncharacterized bacteria facilitate their study and are essential for genetic manipulation. We report new growth media and culture techniques for Caldicellulosiruptor bescii, the most thermophilic cellulolytic bacterium known. A low osmolarity defined growth medium (LOD) was developed that avoids problems associated with precipitates that form in previously reported media allowing the monitoring of culture density by optical density at 680 nm (OD(680)) and more efficient DNA transformation by electroporation. This is a defined minimal medium and does not support growth when a carbon source is omitted, making it suitable for selection of nutritional markers as well as the study of biomass utilization by C. bescii. A low osmolarity complex growth medium (LOC) was developed that dramatically improves growth and culture viability during storage, making it a better medium for routine growth and passaging of C. bescii. Both media contain significantly lower solute concentration than previously published media, allowing for flexibility in developing more specialized media types while avoiding the issues of growth inhibition and cell lysis due to osmotic stress. Plating on LOD medium solidified by agar results in ~1,000-fold greater plating efficiency than previously reported and allows the isolation of discrete colonies. These new media represent a significant advance for both genetic manipulation and the study of biomass utilization in C. bescii, and may be applied broadly across the Caldicellulosiruptor genus.
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Willquist K, Pawar SS, Van Niel EWJ. Reassessment of hydrogen tolerance in Caldicellulosiruptor saccharolyticus. Microb Cell Fact 2011; 10:111. [PMID: 22189215 PMCID: PMC3339340 DOI: 10.1186/1475-2859-10-111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2011] [Accepted: 12/21/2011] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Caldicellulosiruptor saccharolyticus has the ability to produce hydrogen (H2) at high yields from a wide spectrum of carbon sources, and has therefore gained industrial interest. For a cost-effective biohydrogen process, the ability of an organism to tolerate high partial pressures of H2 (PH2) is a critical aspect to eliminate the need for continuous stripping of the produced H2 from the bioreactor. RESULTS Herein, we demonstrate that, under given conditions, growth and H2 production in C. saccharolyticus can be sustained at PH2 up to 67 kPa in a chemostat. At this PH2, 38% and 16% of the pyruvate flux was redirected to lactate and ethanol, respectively, to maintain a relatively low cytosolic NADH/NAD ratio (0.12 mol/mol). To investigate the effect of the redox ratio on the glycolytic flux, a kinetic model describing the activity of the key glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was developed. Indeed, at NADH/NAD ratios of 0.12 mol/mol (Ki of NADH = 0.03 ± 0.01 mM) GAPDH activity was inhibited by only 50% allowing still a high glycolytic flux (3.2 ± 0.4 mM/h). Even at high NADH/NAD ratios up to 1 mol/mol the enzyme was not completely inhibited. During batch cultivations, hydrogen tolerance of C. saccharolyticus was dependent on the growth phase of the organism as well as the carbon and energy source used. The obtained results were analyzed, based on thermodynamic and enzyme kinetic considerations, to gain insight in the mechanism underlying the unique ability of C. saccharolyticus to grow and produce H2 under relatively high PH2. CONCLUSION C. saccharolyticus is able to grow and produce hydrogen at high PH2, hence eliminating the need of gas sparging in its cultures. Under this condition, it has a unique ability to fine tune its metabolism by maintaining the glycolytic flux through regulating GAPDH activity and redistribution of pyruvate flux. Concerning the later, xylose-rich feedstock should be preferred over the sucrose-rich one for better H2 yield.
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Affiliation(s)
- Karin Willquist
- Department of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Sudhanshu S Pawar
- Department of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Ed WJ Van Niel
- Department of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
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