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Jia D, Deng W, Hu P, Jiang W, Gu Y. Thermophilic Moorella thermoacetica as a platform microorganism for C1 gas utilization: physiology, engineering, and applications. BIORESOUR BIOPROCESS 2023; 10:61. [PMID: 38647965 PMCID: PMC10992200 DOI: 10.1186/s40643-023-00682-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 08/29/2023] [Indexed: 04/25/2024] Open
Abstract
In the context of the rapid development of low-carbon economy, there has been increasing interest in utilizing naturally abundant and cost-effective one-carbon (C1) substrates for sustainable production of chemicals and fuels. Moorella thermoacetica, a model acetogenic bacterium, has attracted significant attention due to its ability to utilize carbon dioxide (CO2) and carbon monoxide (CO) via the Wood-Ljungdahl (WL) pathway, thereby showing great potential for the utilization of C1 gases. However, natural strains of M. thermoacetica are not yet fully suitable for industrial applications due to their limitations in carbon assimilation and conversion efficiency as well as limited product range. Over the past decade, progresses have been made in the development of genetic tools for M. thermoacetica, accelerating the understanding and modification of this acetogen. Here, we summarize the physiological and metabolic characteristics of M. thermoacetica and review the recent advances in engineering this bacterium. Finally, we propose the future directions for exploring the real potential of M. thermoacetica in industrial applications.
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Affiliation(s)
- Dechen Jia
- CAS-Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wangshuying Deng
- CAS-Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Peng Hu
- Shanghai GTLB Biotech Co., Ltd, 1688 North Guoquan Road, Shanghai, 200438, China
| | - Weihong Jiang
- CAS-Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yang Gu
- CAS-Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China.
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Ortiz-Medina JF, Poole MR, Grunden AM, Call DF. Nitrogen Fixation and Ammonium Assimilation Pathway Expression of Geobacter sulfurreducens Changes in Response to the Anode Potential in Microbial Electrochemical Cells. Appl Environ Microbiol 2023; 89:e0207322. [PMID: 36975810 PMCID: PMC10132095 DOI: 10.1128/aem.02073-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 03/07/2023] [Indexed: 03/29/2023] Open
Abstract
Nitrogen gas (N2) fixation in the anode-respiring bacterium Geobacter sulfurreducens occurs through complex, multistep processes. Optimizing ammonium (NH4+) production from this bacterium in microbial electrochemical technologies (METs) requires an understanding of how those processes are regulated in response to electrical driving forces. In this study, we quantified gene expression levels (via RNA sequencing) of G. sulfurreducens growing on anodes fixed at two different potentials (-0.15 V and +0.15 V versus standard hydrogen electrode). The anode potential had a significant impact on the expression levels of N2 fixation genes. At -0.15 V, the expression of nitrogenase genes, such as nifH, nifD, and nifK, significantly increased relative to that at +0.15 V, as well as genes associated with NH4+ uptake and transformation, such as glutamine and glutamate synthetases. Metabolite analysis confirmed that both of these organic compounds were present in significantly higher intracellular concentrations at -0.15 V. N2 fixation rates (estimated using the acetylene reduction assay and normalized to total protein) were significantly larger at -0.15 V. Genes expressing flavin-based electron bifurcation complexes, such as electron-transferring flavoproteins (EtfAB) and the NADH-dependent ferredoxin:NADP reductase (NfnAB), were also significantly upregulated at -0.15 V, suggesting that these mechanisms may be involved in N2 fixation at that potential. Our results show that in energy-constrained situations (i.e., low anode potential), the cells increase per-cell respiration and N2 fixation rates. We hypothesize that at -0.15 V, they increase N2 fixation activity to help maintain redox homeostasis, and they leverage electron bifurcation as a strategy to optimize energy generation and use. IMPORTANCE Biological nitrogen fixation coupled with ammonium recovery provides a sustainable alternative to the carbon-, water-, and energy-intensive Haber-Bosch process. Aerobic biological nitrogen fixation technologies are hindered by oxygen gas inhibition of the nitrogenase enzyme. Electrically driving biological nitrogen fixation in anaerobic microbial electrochemical technologies overcomes this challenge. Using Geobacter sulfurreducens as a model exoelectrogenic diazotroph, we show that the anode potential in microbial electrochemical technologies has a significant impact on nitrogen gas fixation rates, ammonium assimilation pathways, and expression of genes associated with nitrogen gas fixation. These findings have important implications for understanding regulatory pathways of nitrogen gas fixation and will help identify target genes and operational strategies to enhance ammonium production in microbial electrochemical technologies.
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Affiliation(s)
- Juan F. Ortiz-Medina
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Mark R. Poole
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Amy M. Grunden
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Douglas F. Call
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
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Schulz S, Molitor B, Angenent LT. Acetate augmentation boosts the ethanol production rate and specificity by Clostridium ljungdahlii during gas fermentation with pure carbon monoxide. BIORESOURCE TECHNOLOGY 2023; 369:128387. [PMID: 36435417 DOI: 10.1016/j.biortech.2022.128387] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 11/20/2022] [Accepted: 11/21/2022] [Indexed: 06/16/2023]
Abstract
Recycling waste gases from industry is vital for the transition toward a circular economy. The model microbe Clostridium ljungdahlii reduces carbon from syngas and primarily produces acetate and ethanol. Here, a gas fermentation experiment is presented in chemostats with C. ljungdahlii and pure carbon monoxide (CO) as feedstock while entirely omitting yeast extract. A maximum ethanol production rate of 0.07 ± 0.01 g L-1 h-1 and a maximum average ethanol/acetate ratio of 1.41 ± 0.39 was observed under steady-state conditions. This confirmed that CO as the sole feedstock pushes the metabolism toward more reduced fermentation products. This effect was even more pronounced when 15 mM sodium acetate was added to the feed medium. An ethanol production rate of 0.23 ± 0.01 g L-1 h-1 was achieved, representing an increase of more than 240%. This increase was accompanied by an increase in cell density and selectivity toward ethanol, with a maximum average ethanol/acetate ratio of 92.96 ± 28.39. Oxygen contaminations voided this effect, although the cultures were still able to maintain a stable biomass concentration and ethanol production rate. These findings highlight the potential of CO-fermentation with acetate augmentation and the importance of preventing oxygen contaminations.
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Affiliation(s)
- Sarah Schulz
- Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany
| | - Bastian Molitor
- Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany; Cluster of Excellence - Controlling Microbes to Fight Infections, University of Tübingen, Germany
| | - Largus T Angenent
- Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany; Cluster of Excellence - Controlling Microbes to Fight Infections, University of Tübingen, Germany; AG Angenent, Max Planck Institute for Biology Tübingen, Max Planck Ring 5, 72076 Tübingen, Germany; Department of Biological and Chemical Engineering, Aarhus University, Universitetsbyen 36, 8000 Aarhus C, Denmark; The Novo Nordisk Foundation CO(2) Research Center (CORC), Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
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Inoue M, Omae K, Nakamoto I, Kamikawa R, Yoshida T, Sako Y. Biome-specific distribution of Ni-containing carbon monoxide dehydrogenases. Extremophiles 2022; 26:9. [PMID: 35059858 PMCID: PMC8776680 DOI: 10.1007/s00792-022-01259-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 01/04/2022] [Indexed: 11/24/2022]
Abstract
Ni-containing carbon monoxide dehydrogenase (Ni-CODH) plays an important role in the CO/CO2-based carbon and energy metabolism of microbiomes. Ni-CODH is classified into distinct phylogenetic clades, A–G, with possibly distinct cellular roles. However, the types of Ni-CODH clade used by organisms in different microbiomes are unknown. Here, we conducted a metagenomic survey of a protein database to determine the relationship between the phylogeny and biome distribution of Ni-CODHs. Clustering and phylogenetic analyses showed that the metagenome assembly-derived Ni-CODH sequences were distributed in ~ 60% Ni-CODH clusters and in all Ni-CODH clades. We also identified a novel Ni-CODH clade, clade H. Biome mapping on the Ni-CODH phylogenetic tree revealed that Ni-CODHs of almost all the clades were found in natural aquatic environmental and engineered samples, whereas those of specific subclades were found only in host-associated samples. These results are comparable with our finding that the diversity in the phylum-level taxonomy of host-associated Ni-CODH owners is statistically different from those of the other biomes. Our findings suggest that while Ni-CODH is a ubiquitous enzyme produced across diverse microbiomes, its distribution in each clade is biased and mainly affected by the distinct composition of microbiomes.
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Affiliation(s)
- Masao Inoue
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan.
- R-GIRO, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
| | - Kimiho Omae
- Department of Integrated Biosciences, Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan
| | - Issei Nakamoto
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Ryoma Kamikawa
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Takashi Yoshida
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Yoshihiko Sako
- Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
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Liu Y, Zhang Z, Jiang W, Gu Y. Protein acetylation-mediated cross-regulation of acetic acid and ethanol synthesis in the gas-fermenting Clostridium ljungdahlii. J Biol Chem 2021; 298:101538. [PMID: 34954142 PMCID: PMC8814400 DOI: 10.1016/j.jbc.2021.101538] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 12/16/2021] [Accepted: 12/20/2021] [Indexed: 01/23/2023] Open
Abstract
The autotrophic acetogen Clostridium ljungdahlii has emerged as a major candidate in the biological conversion of one-carbon gases (CO2/CO) to bulk chemicals and fuels. Nevertheless, the regulatory pathways and downstream metabolic changes responsible for product formation and distribution in this bacterium remain minimally explored. Protein lysine acetylation (PLA), a prevalent posttranslational modification, controls numerous crucial cellular functions. Herein, we revealed a novel cross-regulatory mechanism that uses both the PLA system and transcription factors to regulate the carbon flow distribution for product formation in C. ljungdahlii. The dominant acetylation/deacetylation system (At2/Dat1) in C. ljungdahlii was found to regulate the ratio of two major products, acetic acid and ethanol. Subsequent genetic and biochemical analyses revealed that the activities of Pta and AdhE1, two crucial enzymes responsible for acetic acid and ethanol synthesis, respectively, were greatly affected by their levels of PLA. We found that the acetylation statuses of Pta and AdhE1 underwent significant dynamic changes during the fermentation process, leading to differential synthesis of acetic acid and ethanol. Furthermore, the crucial redox-sensing protein Rex was shown to be regulated by PLA, which subsequently altered its transcriptional regulation on genes responsible for acetic acid and ethanol formation and distribution. Based on our understanding of this cross-regulatory module, we optimized the ethanol synthetic pathway by modifying the acetylation status (deacetylation-mimicked mutations of crucial lysine residues) of the related key enzyme, achieving significantly increased titer and yield of ethanol, an important chemical and fuel, by C. ljungdahlii in gas fermentation.
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Affiliation(s)
- Yanqiang Liu
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ziwen Zhang
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Weihong Jiang
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China.
| | - Yang Gu
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China.
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When anaerobes encounter oxygen: mechanisms of oxygen toxicity, tolerance and defence. Nat Rev Microbiol 2021; 19:774-785. [PMID: 34183820 PMCID: PMC9191689 DOI: 10.1038/s41579-021-00583-y] [Citation(s) in RCA: 84] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2021] [Indexed: 02/06/2023]
Abstract
The defining trait of obligate anaerobes is that oxygen blocks their growth, yet the underlying mechanisms are unclear. A popular hypothesis was that these microorganisms failed to evolve defences to protect themselves from reactive oxygen species (ROS) such as superoxide and hydrogen peroxide, and that this failure is what prevents their expansion to oxic habitats. However, studies reveal that anaerobes actually wield most of the same defences that aerobes possess, and many of them have the capacity to tolerate substantial levels of oxygen. Therefore, to understand the structures and real-world dynamics of microbial communities, investigators have examined how anaerobes such as Bacteroides, Desulfovibrio, Pyrococcus and Clostridium spp. struggle and cope with oxygen. The hypoxic environments in which these organisms dwell - including the mammalian gut, sulfur vents and deep sediments - experience episodic oxygenation. In this Review, we explore the molecular mechanisms by which oxygen impairs anaerobes and the degree to which bacteria protect their metabolic pathways from it. The emergent view of anaerobiosis is that optimal strategies of anaerobic metabolism depend upon radical chemistry and low-potential metal centres. Such catalytic sites are intrinsically vulnerable to direct poisoning by molecular oxygen and ROS. Observations suggest that anaerobes have evolved tactics that either minimize the extent to which oxygen disrupts their metabolism or restore function shortly after the stress has dissipated.
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Jia D, He M, Tian Y, Shen S, Zhu X, Wang Y, Zhuang Y, Jiang W, Gu Y. Metabolic Engineering of Gas-Fermenting Clostridium ljungdahlii for Efficient Co-production of Isopropanol, 3-Hydroxybutyrate, and Ethanol. ACS Synth Biol 2021; 10:2628-2638. [PMID: 34549587 DOI: 10.1021/acssynbio.1c00235] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rational design and modification of autotrophic bacteria to efficiently produce high-value chemicals and biofuels are crucial for establishing a sustainable and economically viable process for one-carbon (C1) source utilization, which, however, remains a challenge in metabolic engineering. In this study, autotrophic Clostridium ljungdahlii was metabolically engineered to efficiently co-produce three important bulk chemicals, isopropanol, 3-hydroxybutyrate (3-HB), and ethanol (together, IHE), using syngas (CO2/CO). An artificial isopropanol-producing pathway was first constructed and optimized in C. ljungdahlii to achieve an efficient production of isopropanol and an unexpected product, 3-HB. Based on this finding, an endogenous active dehydrogenase capable of converting acetoacetate to 3-HB was identified in C. ljungdahlii, thereby revealing an efficient 3-HB-producing pathway. The engineered strain was further optimized to reassimilate acetic acid and synthesize 3-HB by introducing heterologous functional genes. Finally, the best-performing strain was able to produce 13.4, 3.0, and 28.4 g/L of isopropanol, 3-HB, and ethanol, respectively, in continuous gas fermentation. Therefore, this work represents remarkable progress in microbial production of bulk chemicals using C1 gases.
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Affiliation(s)
- Dechen Jia
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Meiyu He
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
- Key Laboratory of Plant Stress Biology, State Key Laboratory of Cotton Biology, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Yi Tian
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
- Key Laboratory of Plant Stress Biology, State Key Laboratory of Cotton Biology, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Shaohuang Shen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Xianfeng Zhu
- Key Laboratory of Plant Stress Biology, State Key Laboratory of Cotton Biology, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Yonghong Wang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yingping Zhuang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Weihong Jiang
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yang Gu
- Key Laboratory of Synthetic Biology, The State Key Laboratory of Plant Carbon-Nitrogen Assimilation, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
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Baleeiro FCF, Ardila MS, Kleinsteuber S, Sträuber H. Effect of Oxygen Contamination on Propionate and Caproate Formation in Anaerobic Fermentation. Front Bioeng Biotechnol 2021; 9:725443. [PMID: 34568301 PMCID: PMC8460912 DOI: 10.3389/fbioe.2021.725443] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 08/19/2021] [Indexed: 01/19/2023] Open
Abstract
Mixed microbial cultures have become a preferred choice of biocatalyst for chain elongation systems due to their ability to convert complex substrates into medium-chain carboxylates. However, the complexity of the effects of process parameters on the microbial metabolic networks is a drawback that makes the task of optimizing product selectivity challenging. Here, we studied the effects of small air contaminations on the microbial community dynamics and the product formation in anaerobic bioreactors fed with lactate, acetate and H2/CO2. Two stirred tank reactors and two bubble column reactors were operated with H2/CO2 gas recirculation for 139 and 116 days, respectively, at pH 6.0 and 32°C with a hydraulic retention time of 14 days. One reactor of each type had periods with air contamination (between 97 ± 28 and 474 ± 33 mL O2 L−1 d−1, lasting from 4 to 32 days), while the control reactors were kept anoxic. During air contamination, production of n-caproate and CH4 was strongly inhibited, whereas no clear effect on n-butyrate production was observed. In a period with detectable O2 concentrations that went up to 18%, facultative anaerobes of the genus Rummeliibacillus became predominant and only n-butyrate was produced. However, at low air contamination rates and with O2 below the detection level, Coriobacteriia and Actinobacteria gained a competitive advantage over Clostridia and Methanobacteria, and propionate production rates increased to 0.8–1.8 mmol L−1 d−1 depending on the reactor (control reactors 0.1–0.8 mmol L−1 d−1). Moreover, i-butyrate production was observed, but only when Methanobacteria abundances were low and, consequently, H2 availability was high. After air contamination stopped completely, production of n-caproate and CH4 recovered, with n-caproate production rates of 1.4–1.8 mmol L−1 d−1 (control 0.7–2.1 mmol L−1 d−1). The results underline the importance of keeping strictly anaerobic conditions in fermenters when consistent n-caproate production is the goal. Beyond that, micro-aeration should be further tested as a controllable process parameter to shape the reactor microbiome. When odd-chain carboxylates are desired, further studies can develop strategies for their targeted production by applying micro-aerobic conditions.
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Affiliation(s)
- Flávio C F Baleeiro
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.,Institute of Process Engineering in Life Science 2, Technical Biology, Karlsruhe Institute of Technology - KIT, Karlsruhe, Germany
| | - Magda S Ardila
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.,Institute of Process Engineering in Life Science 2, Technical Biology, Karlsruhe Institute of Technology - KIT, Karlsruhe, Germany
| | - Sabine Kleinsteuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Heike Sträuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
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Grimalt-Alemany A, Etler C, Asimakopoulos K, Skiadas IV, Gavala HN. ORP control for boosting ethanol productivity in gas fermentation systems and dynamics of redox cofactor NADH/NAD+ under oxidative stress. J CO2 UTIL 2021. [DOI: 10.1016/j.jcou.2021.101589] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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10
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Morvan C, Folgosa F, Kint N, Teixeira M, Martin-Verstraete I. Responses of Clostridia to oxygen: from detoxification to adaptive strategies. Environ Microbiol 2021; 23:4112-4125. [PMID: 34245087 DOI: 10.1111/1462-2920.15665] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/02/2021] [Accepted: 07/07/2021] [Indexed: 11/30/2022]
Abstract
Clostridia comprise bacteria of environmental, biotechnological and medical interest and many commensals of the gut microbiota. Because of their strictly anaerobic lifestyle, oxygen is a major stress for Clostridia. However, recent data showed that these bacteria can cope with O2 better than expected for obligate anaerobes through their ability to scavenge, detoxify and consume O2 . Upon O2 exposure, Clostridia redirect their central metabolism onto pathways less O2 -sensitive and induce the expression of genes encoding enzymes involved in O2 -reduction and in the repair of oxidized damaged molecules. While Faecalibacterium prausnitzii efficiently consumes O2 through a specific extracellular electron shuttling system requiring riboflavin, enzymes such as rubrerythrins and flavodiiron proteins with NAD(P)H-dependent O2 - and/or H2 O2 -reductase activities are usually encoded in other Clostridia. These two classes of enzymes play indeed a pivotal role in O2 tolerance in Clostridioides difficile and Clostridium acetobutylicum. Two main signalling pathways triggering O2 -induced responses have been described so far in Clostridia. PerR acts as a key regulator of the O2 - and/or reactive oxygen species-defence machinery while in C. difficile, σB , the sigma factor of the general stress response also plays a crucial role in O2 tolerance by controlling the expression of genes involved in O2 scavenging and repair systems.
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Affiliation(s)
- Claire Morvan
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, Université de Paris, Paris, F-75015, France
| | - Filipe Folgosa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, 2780-157, Portugal
| | - Nicolas Kint
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, Université de Paris, Paris, F-75015, France
| | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, 2780-157, Portugal
| | - Isabelle Martin-Verstraete
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, Université de Paris, Paris, F-75015, France
- Institut Universitaire de France, Paris, France
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Diallo M, Kengen SWM, López-Contreras AM. Sporulation in solventogenic and acetogenic clostridia. Appl Microbiol Biotechnol 2021; 105:3533-3557. [PMID: 33900426 PMCID: PMC8102284 DOI: 10.1007/s00253-021-11289-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 04/03/2021] [Accepted: 04/07/2021] [Indexed: 02/07/2023]
Abstract
The Clostridium genus harbors compelling organisms for biotechnological production processes; while acetogenic clostridia can fix C1-compounds to produce acetate and ethanol, solventogenic clostridia can utilize a wide range of carbon sources to produce commercially valuable carboxylic acids, alcohols, and ketones by fermentation. Despite their potential, the conversion by these bacteria of carbohydrates or C1 compounds to alcohols is not cost-effective enough to result in economically viable processes. Engineering solventogenic clostridia by impairing sporulation is one of the investigated approaches to improve solvent productivity. Sporulation is a cell differentiation process triggered in bacteria in response to exposure to environmental stressors. The generated spores are metabolically inactive but resistant to harsh conditions (UV, chemicals, heat, oxygen). In Firmicutes, sporulation has been mainly studied in bacilli and pathogenic clostridia, and our knowledge of sporulation in solvent-producing or acetogenic clostridia is limited. Still, sporulation is an integral part of the cellular physiology of clostridia; thus, understanding the regulation of sporulation and its connection to solvent production may give clues to improve the performance of solventogenic clostridia. This review aims to provide an overview of the triggers, characteristics, and regulatory mechanism of sporulation in solventogenic clostridia. Those are further compared to the current knowledge on sporulation in the industrially relevant acetogenic clostridia. Finally, the potential applications of spores for process improvement are discussed.Key Points• The regulatory network governing sporulation initiation varies in solventogenic clostridia.• Media composition and cell density are the main triggers of sporulation.• Spores can be used to improve the fermentation process.
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Affiliation(s)
- Mamou Diallo
- Wageningen Food and Biobased Research, Wageningen, The Netherlands.
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands.
| | - Servé W M Kengen
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
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Lo J, Humphreys JR, Jack J, Urban C, Magnusson L, Xiong W, Gu Y, Ren ZJ, Maness PC. The Metabolism of Clostridium ljungdahlii in Phosphotransacetylase Negative Strains and Development of an Ethanologenic Strain. Front Bioeng Biotechnol 2020; 8:560726. [PMID: 33195125 PMCID: PMC7653027 DOI: 10.3389/fbioe.2020.560726] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 10/05/2020] [Indexed: 11/13/2022] Open
Abstract
The sustainable production of chemicals from non-petrochemical sources is one of the greatest challenges of our time. CO2 release from industrial activity is not environmentally friendly yet provides an inexpensive feedstock for chemical production. One means of addressing this problem is using acetogenic bacteria to produce chemicals from CO2, waste streams, or renewable resources. Acetogens are attractive hosts for chemical production for many reasons: they can utilize a variety of feedstocks that are renewable or currently waste streams, can capture waste carbon sources and covert them to products, and can produce a variety of chemicals with greater carbon efficiency over traditional fermentation technologies. Here we investigated the metabolism of Clostridium ljungdahlii, a model acetogen, to probe carbon and electron partitioning and understand what mechanisms drive product formation in this organism. We utilized CRISPR/Cas9 and an inducible riboswitch to target enzymes involved in fermentation product formation. We focused on the genes encoding phosphotransacetylase (pta), aldehyde ferredoxin oxidoreductases (aor1 and aor2), and bifunctional alcohol/aldehyde dehydrogenases (adhE1 and adhE2) and performed growth studies under a variety of conditions to probe the role of those enzymes in the metabolism. Finally, we demonstrated a switch from acetogenic to ethanologenic metabolism by these manipulations, providing an engineered bacterium with greater application potential in biorefinery industry.
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Affiliation(s)
- Jonathan Lo
- National Renewable Energy Laboratory, Golden, CO, United States
| | | | - Joshua Jack
- Andlinger Center for Energy and Environment, Princeton University, Princeton, NJ, United States
| | - Chris Urban
- National Renewable Energy Laboratory, Golden, CO, United States
| | | | - Wei Xiong
- National Renewable Energy Laboratory, Golden, CO, United States
| | - Yang Gu
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Zhiyong Jason Ren
- Andlinger Center for Energy and Environment, Princeton University, Princeton, NJ, United States
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Synthetic Biology on Acetogenic Bacteria for Highly Efficient Conversion of C1 Gases to Biochemicals. Int J Mol Sci 2020; 21:ijms21207639. [PMID: 33076477 PMCID: PMC7589590 DOI: 10.3390/ijms21207639] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/13/2020] [Accepted: 10/13/2020] [Indexed: 12/13/2022] Open
Abstract
Synthesis gas, which is mainly produced from fossil fuels or biomass gasification, consists of C1 gases such as carbon monoxide, carbon dioxide, and methane as well as hydrogen. Acetogenic bacteria (acetogens) have emerged as an alternative solution to recycle C1 gases by converting them into value-added biochemicals using the Wood-Ljungdahl pathway. Despite the advantage of utilizing acetogens as biocatalysts, it is difficult to develop industrial-scale bioprocesses because of their slow growth rates and low productivities. To solve these problems, conventional approaches to metabolic engineering have been applied; however, there are several limitations owing to the lack of required genetic bioparts for regulating their metabolic pathways. Recently, synthetic biology based on genetic parts, modules, and circuit design has been actively exploited to overcome the limitations in acetogen engineering. This review covers synthetic biology applications to design and build industrial platform acetogens.
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Nissen LS, Basen M. The emerging role of aldehyde:ferredoxin oxidoreductases in microbially-catalyzed alcohol production. J Biotechnol 2019; 306:105-117. [DOI: 10.1016/j.jbiotec.2019.09.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/09/2019] [Accepted: 09/09/2019] [Indexed: 11/16/2022]
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Type E Botulinum Neurotoxin-Producing Clostridium butyricum Strains Are Aerotolerant during Vegetative Growth. mSystems 2019; 4:mSystems00299-18. [PMID: 31058231 PMCID: PMC6495232 DOI: 10.1128/msystems.00299-18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 04/10/2019] [Indexed: 11/21/2022] Open
Abstract
Botulinum neurotoxins, the causative agents of the potentially fatal disease of botulism, are produced by certain Clostridium strains during vegetative growth, usually in anaerobic environments. Our findings indicate that, contrary to current understanding, the growth of neurotoxigenic C. butyricum strains and botulinum neurotoxin type E production can continue upon transfer from anaerobic to aerated conditions and that adaptation of strains to oxygenated environments requires global changes in proteomic and metabolic profiles. We hypothesize that aerotolerance might constitute an unappreciated factor conferring physiological advantages on some botulinum toxin-producing clostridial strains, allowing them to adapt to otherwise restrictive environments. Clostridium butyricum, the type species of the genus Clostridium, is considered an obligate anaerobe, yet it has been shown to grow in the presence of oxygen. C. butyricum strains atypically producing the botulinum neurotoxin type E are the leading cause of type E human botulism in Italy. Here, we show that type E botulinum neurotoxin-producing C. butyricum strains growing exponentially were able to keep growing and producing toxin in vitro upon exposure to air, although less efficiently than under ideal oxygen-depleted conditions. Bacterial growth in air was maintained when the initial cell density was higher than 103 cells/ml. No spores were detected in the cultures aerated for 5 h. To understand the biological mechanisms allowing the adaptation of vegetative cells of C. butyricum type E to oxygen, we compared the proteome and metabolome profiles of the clostridial cultures grown for 5 h under either aerated or anaerobic conditions. The results indicated that bacterial cells responded to oxygen stress by slowing growth and modulating the expression of proteins involved in carbohydrate uptake and metabolism, redox homeostasis, DNA damage response, and bacterial motility. Moreover, the ratio of acetate to butyrate was significantly higher under aeration. This study demonstrates for the first time that a botulinum neurotoxin-producing Clostridium can withstand oxygen during vegetative growth. IMPORTANCE Botulinum neurotoxins, the causative agents of the potentially fatal disease of botulism, are produced by certain Clostridium strains during vegetative growth, usually in anaerobic environments. Our findings indicate that, contrary to current understanding, the growth of neurotoxigenic C. butyricum strains and botulinum neurotoxin type E production can continue upon transfer from anaerobic to aerated conditions and that adaptation of strains to oxygenated environments requires global changes in proteomic and metabolic profiles. We hypothesize that aerotolerance might constitute an unappreciated factor conferring physiological advantages on some botulinum toxin-producing clostridial strains, allowing them to adapt to otherwise restrictive environments.
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Inoue M, Nakamoto I, Omae K, Oguro T, Ogata H, Yoshida T, Sako Y. Structural and Phylogenetic Diversity of Anaerobic Carbon-Monoxide Dehydrogenases. Front Microbiol 2019; 9:3353. [PMID: 30705673 PMCID: PMC6344411 DOI: 10.3389/fmicb.2018.03353] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 12/31/2018] [Indexed: 11/30/2022] Open
Abstract
Anaerobic Ni-containing carbon-monoxide dehydrogenases (Ni-CODHs) catalyze the reversible conversion between carbon monoxide and carbon dioxide as multi-enzyme complexes responsible for carbon fixation and energy conservation in anaerobic microbes. However, few biochemically characterized model enzymes exist, with most Ni-CODHs remaining functionally unknown. Here, we performed phylogenetic and structure-based Ni-CODH classification using an expanded dataset comprised of 1942 non-redundant Ni-CODHs from 1375 Ni-CODH-encoding genomes across 36 phyla. Ni-CODHs were divided into seven clades, including a novel clade. Further classification into 24 structural groups based on sequence analysis combined with structural prediction revealed diverse structural motifs for metal cluster formation and catalysis, including novel structural motifs potentially capable of forming metal clusters or binding metal ions, indicating Ni-CODH diversity and plasticity. Phylogenetic analysis illustrated that the metal clusters responsible for intermolecular electron transfer were drastically altered during evolution. Additionally, we identified novel putative Ni-CODH-associated proteins from genomic contexts other than the Wood–Ljungdahl pathway and energy converting hydrogenase system proteins. Network analysis among the structural groups of Ni-CODHs, their associated proteins and taxonomies revealed previously unrecognized gene clusters for Ni-CODHs, including uncharacterized structural groups with putative metal transporters, oxidoreductases, or transcription factors. These results suggested diversification of Ni-CODH structures adapting to their associated proteins across microbial genomes.
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Affiliation(s)
- Masao Inoue
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Issei Nakamoto
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Kimiho Omae
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Tatsuki Oguro
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Hiroyuki Ogata
- Institute for Chemical Research, Kyoto University, Kyoto, Japan
| | - Takashi Yoshida
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yoshihiko Sako
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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Li H, Mei X, Liu B, Xie G, Ren N, Xing D. Quantitative proteomic analysis reveals the ethanologenic metabolism regulation of Ethanoligenens harbinense by exogenous ethanol addition. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:166. [PMID: 31297154 PMCID: PMC6598285 DOI: 10.1186/s13068-019-1511-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 06/19/2019] [Indexed: 05/21/2023]
Abstract
BACKGROUND H2-ethanol-coproducing bacteria, as primary fermenters, play important roles in the microbiome of bioreactors for bioenergy production from organic wastewater or solid wastes. Ethanoligenens harbinense YUAN-3 is an anaerobic ethanol-H2-fermenting bacterium. Ethanol is one of the main end-products of strain YUAN-3 that influence its fermentative process. Until recently, the molecular mechanism of metabolic regulation in strain YUAN-3 during ethanol accumulation has still been unclear. This study aims to elucidate the metabolic regulation mechanisms in strain YUAN-3, which contributes to effectively shape the microbiome for biofuel and bioenergy production from waste stream. RESULTS This study reports that ethanol stress altered the distribution of end-product yields in the H2-ethanol-coproducing Ethanoligenens harbinense strain YUAN-3. Decreasing trends of hydrogen yield from 1888.6 ± 45.8 to 837 ± 64.7 mL L-1 and acetic acid yield from 1767.7 ± 45 to 160.6 ± 44.7 mg L-1 were observed in strain YUAN-3 with increasing exogenous ethanol (0 mM-200 mM). However, the ethanol yield of strain YUAN-3 increased by 15.1%, 30.1%, and 27.4% in 50 mM, 100 mM, and 200 mM ethanol stress, respectively. The endogenous ethanol accounted for 96.1% (w/w) in liquid end-products when exogenous ethanol of 200 mM was added. The molar ratio of ethanol to acetic acid increased 14 times (exogenous ethanol of 200 mM) compared to the control. iTRAQ-based quantitative proteomic analysis indicated that 263 proteins of strain YUAN-3 were differentially expressed in 50 mM, 100 mM, and 200 mM of exogenous ethanol. These proteins are mainly involved in amino acid transport and metabolism, central carbon metabolism, and oxidative stress response. CONCLUSION These differentially expressed proteins play important roles in metabolic changes necessary for growth and survival of strain YUAN-3 during ethanol stress. The up-regulation of bifunctional acetaldehyde-CoA/alcohol dehydrogenase (ADHE) was the main reason why ethanol production was enhanced, while hydrogen gas and acetic acid yields declined in strain YUAN-3 during ethanol stress. This study also provides a new approach for the enhancement of ethanologenesis by H2-ethanol-coproducing bacteria through exogenous ethanol addition.
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Affiliation(s)
- Huahua Li
- State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, P.O. Box 2614, No. 73 Huanghe Road, Nangang District, Harbin, 150090 Heilongjiang China
| | - Xiaoxue Mei
- State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, P.O. Box 2614, No. 73 Huanghe Road, Nangang District, Harbin, 150090 Heilongjiang China
| | - Bingfeng Liu
- State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, P.O. Box 2614, No. 73 Huanghe Road, Nangang District, Harbin, 150090 Heilongjiang China
| | - Guojun Xie
- State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, P.O. Box 2614, No. 73 Huanghe Road, Nangang District, Harbin, 150090 Heilongjiang China
| | - Nanqi Ren
- State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, P.O. Box 2614, No. 73 Huanghe Road, Nangang District, Harbin, 150090 Heilongjiang China
| | - Defeng Xing
- State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, P.O. Box 2614, No. 73 Huanghe Road, Nangang District, Harbin, 150090 Heilongjiang China
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Jarboe LR. Improving the success and impact of the metabolic engineering design, build, test, learn cycle by addressing proteins of unknown function. Curr Opin Biotechnol 2018; 53:93-98. [PMID: 29306676 DOI: 10.1016/j.copbio.2017.12.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 12/12/2017] [Accepted: 12/17/2017] [Indexed: 12/20/2022]
Abstract
Rational, predictive metabolic engineering of organisms requires an ability to associate biological activity to the corresponding gene(s). Despite extensive advances in the 20 years since the Escherichia coli genome was published, there are still gaps in our knowledge of protein function. The substantial amount of data that has been published, such as: omics-level characterization in a myriad of conditions; genome-scale libraries; and evolution and genome sequencing, provide means of identifying and prioritizing proteins for characterization. This review describes the scale of this knowledge gap, demonstrates the benefit of addressing the knowledge gap, and demonstrates the availability of interesting candidates for characterization.
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Affiliation(s)
- Laura R Jarboe
- Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, United States; Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA 50011, United States.
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19
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Bengelsdorf FR, Beck MH, Erz C, Hoffmeister S, Karl MM, Riegler P, Wirth S, Poehlein A, Weuster-Botz D, Dürre P. Bacterial Anaerobic Synthesis Gas (Syngas) and CO 2+H 2 Fermentation. ADVANCES IN APPLIED MICROBIOLOGY 2018; 103:143-221. [PMID: 29914657 DOI: 10.1016/bs.aambs.2018.01.002] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Anaerobic bacterial gas fermentation gains broad interest in various scientific, social, and industrial fields. This microbial process is carried out by a specific group of bacterial strains called acetogens. All these strains employ the Wood-Ljungdahl pathway but they belong to different taxonomic groups. Here we provide an overview of the metabolism of acetogens and naturally occurring products. Characteristics of 61 strains were summarized and selected acetogens described in detail. Acetobacterium woodii, Clostridium ljungdahlii, and Moorella thermoacetica serve as model organisms. Results of approaches such as genome-scale modeling, proteomics, and transcriptomics are discussed. Metabolic engineering of acetogens can be used to expand the product portfolio to platform chemicals and to study different aspects of cell physiology. Moreover, the fermentation of gases requires specific reactor configurations and the development of the respective technology, which can be used for an industrial application. Even though the overall process will have a positive effect on climate, since waste and greenhouse gases could be converted into commodity chemicals, some legislative barriers exist, which hamper successful exploitation of this technology.
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Affiliation(s)
- Frank R Bengelsdorf
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany.
| | - Matthias H Beck
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Catarina Erz
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Sabrina Hoffmeister
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Michael M Karl
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Peter Riegler
- Technical University of Munich, Institute of Biochemical Engineering, Garching, Germany
| | - Steffen Wirth
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Anja Poehlein
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University, Göttingen, Germany
| | - Dirk Weuster-Botz
- Technical University of Munich, Institute of Biochemical Engineering, Garching, Germany
| | - Peter Dürre
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
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Transcriptomic profiles of Clostridium ljungdahlii during lithotrophic growth with syngas or H 2 and CO 2 compared to organotrophic growth with fructose. Sci Rep 2017; 7:13135. [PMID: 29030620 PMCID: PMC5640608 DOI: 10.1038/s41598-017-12712-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 09/14/2017] [Indexed: 01/13/2023] Open
Abstract
Clostridium ljungdahlii derives energy by lithotrophic and organotrophic acetogenesis. C. ljungdahlii was grown organotrophically with fructose and also lithotrophically, either with syngas - a gas mixture containing hydrogen (H2), carbon dioxide (CO2), and carbon monoxide (CO), or with H2 and CO2. Gene expression was compared quantitatively by microarrays using RNA extracted from all three conditions. Gene expression with fructose and with H2/CO2 was compared by RNA-Seq. Upregulated genes with both syngas and H2/CO2 (compared to fructose) point to the urea cycle, uptake and degradation of peptides and amino acids, response to sulfur starvation, potentially NADPH-producing pathways involving (S)-malate and ornithine, quorum sensing, sporulation, and cell wall remodeling, suggesting a global and multicellular response to lithotrophic conditions. With syngas, the upregulated (R)-lactate dehydrogenase gene represents a route of electron transfer from ferredoxin to NAD. With H2/CO2, flavodoxin and histidine biosynthesis genes were upregulated. Downregulated genes corresponded to an intracytoplasmic microcompartment for disposal of methylglyoxal, a toxic byproduct of glycolysis, as 1-propanol. Several cytoplasmic and membrane-associated redox-active protein genes were differentially regulated. The transcriptomic profiles of C. ljungdahlii in lithotrophic and organotrophic growth modes indicate large-scale physiological and metabolic differences, observations that may guide biofuel and commodity chemical production with this species.
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Shen S, Gu Y, Chai C, Jiang W, Zhuang Y, Wang Y. Enhanced alcohol titre and ratio in carbon monoxide-rich off-gas fermentation of Clostridium carboxidivorans through combination of trace metals optimization with variable-temperature cultivation. BIORESOURCE TECHNOLOGY 2017; 239:236-243. [PMID: 28521234 DOI: 10.1016/j.biortech.2017.04.099] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 04/23/2017] [Accepted: 04/24/2017] [Indexed: 06/07/2023]
Abstract
Bioconversion of C1 gases to produce chemicals has good application prospects. Here, the combination of trace metals optimization using a statistical method with variable-temperature cultivation was used to enhance alcohol synthesis during CO-rich off-gas fermentation by Clostridium carboxidivorans P7. Based on ATCC medium 1754, the optimum concentration of the trace metals was found to be 5-fold Ni2+, Co2+, SeO42+, and WO42+; 3.48-fold Cu2+; 0.55-fold MoO42+; 0.5-fold Zn2+ and (NH4)2SO4·FeSO4·6H2O; and additional 44.32μM FeCl3·6H2O. The production of alcohol and organic acid changed to 4.40g/L and 0.50g/L from 2.16g/L and 2.37g/L, respectively, yielding an increase of alcohol-to-product ratio from 47.7% to 89.8%. By fermenting with the optimized medium and timed control of the incubation temperature (37°C [0-24h]-25°C [24-144h]), the alcohol titre further increased to 6.97g/L with 1.67g/L butanol and 1.33g/L hexanol, exceeding those previously reported for strain P7.
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Affiliation(s)
- Shaohuang Shen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yang Gu
- Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Changsheng Chai
- Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Weihong Jiang
- Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yingping Zhuang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yonghong Wang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
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Heijstra BD, Leang C, Juminaga A. Gas fermentation: cellular engineering possibilities and scale up. Microb Cell Fact 2017; 16:60. [PMID: 28403896 PMCID: PMC5389167 DOI: 10.1186/s12934-017-0676-y] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 04/04/2017] [Indexed: 12/11/2022] Open
Abstract
Low carbon fuels and chemicals can be sourced from renewable materials such as biomass or from industrial and municipal waste streams. Gasification of these materials allows all of the carbon to become available for product generation, a clear advantage over partial biomass conversion into fermentable sugars. Gasification results into a synthesis stream (syngas) containing carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2) and nitrogen (N2). Autotrophy-the ability to fix carbon such as CO2 is present in all domains of life but photosynthesis alone is not keeping up with anthropogenic CO2 output. One strategy is to curtail the gaseous atmospheric release by developing waste and syngas conversion technologies. Historically microorganisms have contributed to major, albeit slow, atmospheric composition changes. The current status and future potential of anaerobic gas-fermenting bacteria with special focus on acetogens are the focus of this review.
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Affiliation(s)
| | - Ching Leang
- LanzaTech, Inc., 8045 Lamon Ave, Suite 400, Skokie, IL USA
| | - Alex Juminaga
- LanzaTech, Inc., 8045 Lamon Ave, Suite 400, Skokie, IL USA
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Pisapia C, Gérard E, Gérard M, Lecourt L, Lang SQ, Pelletier B, Payri CE, Monnin C, Guentas L, Postec A, Quéméneur M, Erauso G, Ménez B. Mineralizing Filamentous Bacteria from the Prony Bay Hydrothermal Field Give New Insights into the Functioning of Serpentinization-Based Subseafloor Ecosystems. Front Microbiol 2017; 8:57. [PMID: 28197130 PMCID: PMC5281578 DOI: 10.3389/fmicb.2017.00057] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 01/09/2017] [Indexed: 11/13/2022] Open
Abstract
Despite their potential importance as analogs of primitive microbial metabolisms, the knowledge of the structure and functioning of the deep ecosystems associated with serpentinizing environments is hampered by the lack of accessibility to relevant systems. These hyperalkaline environments are depleted in dissolved inorganic carbon (DIC), making the carbon sources and assimilation pathways in the associated ecosystems highly enigmatic. The Prony Bay Hydrothermal Field (PHF) is an active serpentinization site where, similar to Lost City (Mid-Atlantic Ridge), high-pH fluids rich in H2 and CH4 are discharged from carbonate chimneys at the seafloor, but in a shallower lagoonal environment. This study aimed to characterize the subsurface microbial ecology of this environment by focusing on the earliest stages of chimney construction, dominated by the discharge of hydrothermal fluids of subseafloor origin. By jointly examining the mineralogy and the microbial diversity of the conduits of juvenile edifices at the micrometric scale, we find a central role of uncultivated bacteria belonging to the Firmicutes in the ecology of the PHF. These bacteria, along with members of the phyla Acetothermia and Omnitrophica, are identified as the first chimneys inhabitants before archaeal Methanosarcinales. They are involved in the construction and early consolidation of the carbonate structures via organomineralization processes. Their predominance in the most juvenile and nascent hydrothermal chimneys, and their affiliation with environmental subsurface microorganisms, indicate that they are likely discharged with hydrothermal fluids from the subseafloor. They may thus be representative of endolithic serpentinization-based ecosystems, in an environment where DIC is limited. In contrast, heterotrophic and fermentative microorganisms may consume organic compounds from the abiotic by-products of serpentinization processes and/or from life in the deeper subsurface. We thus propose that the Firmicutes identified at PHF may have a versatile metabolism with the capability to use diverse organic compounds from biological or abiotic origin. From that perspective, this study sheds new light on the structure of deep microbial communities living at the energetic edge in serpentinites and may provide an alternative model of the earliest metabolisms.
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Affiliation(s)
- Céline Pisapia
- Geomicrobiology Group, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Centre National de la Recherche ScientifiqueParis, France
- DISCO beamline, Synchrotron SOLEILSaint Aubin, France
| | - Emmanuelle Gérard
- Geomicrobiology Group, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Centre National de la Recherche ScientifiqueParis, France
| | - Martine Gérard
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Institut de Recherche pour le Développement, Université Pierre et Marie CurieParis, France
| | - Léna Lecourt
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Institut de Recherche pour le Développement, Université Pierre et Marie CurieParis, France
| | - Susan Q. Lang
- Department of Earth and Ocean Sciences, School of the Earth, Ocean and Environment, University of South Carolina, ColumbiaSC, USA
| | - Bernard Pelletier
- GIS Grand Observatoire de l’environnement et de la biodiversité terrestre et marine dans le Pacifique Sud, Centre IRD de NouméaNouméa, New Caledonia
| | | | - Christophe Monnin
- Géosciences Environnement Toulouse, Université Paul Sabatier, Centre National de la Recherche Scientifique, Institut de Recherche pour le DéveloppementToulouse, France
| | - Linda Guentas
- UR227 COREUS, Centre IRD de NouméaNouméa, New Caledonia
- Laboratoire Matériaux Polymères Interfaces Environnement Marin EA 4323, Université de ToulonLa Garde, France
- Mediterranean Institute of Oceanography, Centre IRD de NouméaNouméa, New Caledonia
- Laboratoire Insulaire du Vivant et de l’Environnement, Université de la Nouvelle-CalédonieNouméa, New Caledonia
| | - Anne Postec
- Aix Marseille Université, Centre National de la Recherche Scientifique – Institut National des Sciences de L’Univers, Université de Toulon, Institut de Recherche pour le Développement, Mediterranean Institute of OceanographyMarseille, France
| | - Marianne Quéméneur
- Aix Marseille Université, Centre National de la Recherche Scientifique – Institut National des Sciences de L’Univers, Université de Toulon, Institut de Recherche pour le Développement, Mediterranean Institute of OceanographyMarseille, France
| | - Gaël Erauso
- Aix Marseille Université, Centre National de la Recherche Scientifique – Institut National des Sciences de L’Univers, Université de Toulon, Institut de Recherche pour le Développement, Mediterranean Institute of OceanographyMarseille, France
| | - Bénédicte Ménez
- Geomicrobiology Group, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Centre National de la Recherche ScientifiqueParis, France
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Biofilm Formation by Clostridium ljungdahlii Is Induced by Sodium Chloride Stress: Experimental Evaluation and Transcriptome Analysis. PLoS One 2017; 12:e0170406. [PMID: 28118386 PMCID: PMC5261816 DOI: 10.1371/journal.pone.0170406] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 01/04/2017] [Indexed: 01/08/2023] Open
Abstract
The acetogen Clostridium ljungdahlii is capable of syngas fermentation and microbial electrosynthesis. Biofilm formation could benefit both these applications, but was not yet reported for C. ljungdahlii. Biofilm formation does not occur under standard growth conditions, but attachment or aggregation could be induced by different stresses. The strongest biofilm formation was observed with the addition of sodium chloride. After 3 days of incubation, the biomass volume attached to a plastic surface was 20 times higher with than without the addition of 200 mM NaCl to the medium. The addition of NaCl also resulted in biofilm formation on glass, graphite and glassy carbon, the latter two being often used electrode materials for microbial electrosynthesis. Biofilms were composed of extracellular proteins, polysaccharides, as well as DNA, while pilus-like appendages were observed with, but not without, the addition of NaCl. A transcriptome analysis comparing planktonic (no NaCl) and biofilm (NaCl addition) cells showed that C. ljungdahlii coped with the salt stress by the upregulation of the general stress response, Na+ export and osmoprotectant accumulation. A potential role for poly-N-acetylglucosamines and D-alanine in biofilm formation was found. Flagellar motility was downregulated, while putative type IV pili biosynthesis genes were not expressed. Moreover, the gene expression analysis suggested the involvement of the transcriptional regulators LexA, Spo0A and CcpA in stress response and biofilm formation. This study showed that NaCl addition might be a valuable strategy to induce biofilm formation by C. ljungdahlii, which can improve the efficacy of syngas fermentation and microbial electrosynthesis applications.
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Whitham JM, Schulte MJ, Bobay BG, Bruno-Barcena JM, Chinn MS, Flickinger MC, Pawlak JJ, Grunden AM. Characterization of Clostridium ljungdahlii OTA1: a non-autotrophic hyper ethanol-producing strain. Appl Microbiol Biotechnol 2016; 101:1615-1630. [PMID: 27866253 DOI: 10.1007/s00253-016-7978-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 10/27/2016] [Accepted: 10/31/2016] [Indexed: 02/07/2023]
Abstract
A Clostridium ljungdahlii lab-isolated spontaneous-mutant strain, OTA1, has been shown to produce twice as much ethanol as the C. ljungdahlii ATCC 55383 strain when cultured in a mixotrophic medium containing fructose and syngas. Whole-genome sequencing identified four unique single nucleotide polymorphisms (SNPs) in the C. ljungdahlii OTA1 genome. Among these, two SNPs were found in the gene coding for AcsA and HemL, enzymes involved in acetyl-CoA formation from CO/CO2. Homology models of the respective mutated enzymes revealed alterations in the size and hydrogen bonding of the amino acids in their active sites. Failed attempts to grow OTA1 autotrophically suggested that one or both of these mutated genes prevented acetyl-CoA synthesis from CO/CO2, demonstrating that its activity was required for autotrophic growth by C. ljungdahlii. An inoperable Wood-Ljungdahl pathway resulted in higher CO2 and ethanol yields and lower biomass and acetate yields compared to WT for multiple growth conditions including heterotrophic and mixotrophic conditions. The two other SNPs identified in the C. ljungdahlii OTA1 genome were in genes coding for transcriptional regulators (CLJU_c09320 and CLJU_c18110) and were found to be responsible for deregulated expression of co-localized arginine catabolism and 2-deoxy-D-ribose catabolism genes. Growth medium supplementation experiments suggested that increased arginine metabolism and 2-deoxy-D-ribose were likely to have minor effects on biomass and fermentation product yields. In addition, in silico flux balance analysis simulating mixotrophic and heterotrophic conditions showed no change in flux to ethanol when flux through HemL was changed whereas limited flux through AcsA increased the ethanol flux for both simulations. In characterizing the effects of the SNPs identified in the C. ljungdahlii OTA1 genome, a non-autotrophic hyper ethanol-producing strain of C. ljungdahlii was identified that has utility for further physiology and strain performance studies and as a biocatalyst for industrial applications.
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Affiliation(s)
- Jason M Whitham
- Department of Plant and Microbial Biology, North Carolina State University, 4548 Thomas Hall, Campus Box 7615, Raleigh, NC, 27695-7615, USA
| | - Mark J Schulte
- Department of Chemical and Biomolecular Engineering, 196 Golden LEAF Biomanufacturing Training and Education Center, North Carolina State University, Raleigh, NC, 27695, USA
| | - Benjamin G Bobay
- Duke University NMR Center, Duke University Medical Center, Duke University, Durham, NC, 27710, USA
| | - Jose M Bruno-Barcena
- Department of Plant and Microbial Biology, North Carolina State University, 4548 Thomas Hall, Campus Box 7615, Raleigh, NC, 27695-7615, USA
| | - Mari S Chinn
- Department of Biological and Agricultural Engineering, North Carolina State University, 277 Weaver Labs, Campus Box 7625, Raleigh, NC, 27695-7625, USA
| | - Michael C Flickinger
- Department of Chemical and Biomolecular Engineering, 196 Golden LEAF Biomanufacturing Training and Education Center, North Carolina State University, Raleigh, NC, 27695, USA
| | - Joel J Pawlak
- Department of Forest Biomaterials, North Carolina State University, 2028C Biltmore Hall, Campus Box 8001, Raleigh, NC, 27695-8001, USA
| | - Amy M Grunden
- Department of Plant and Microbial Biology, North Carolina State University, 4548 Thomas Hall, Campus Box 7615, Raleigh, NC, 27695-7615, USA.
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Molitor B, Richter H, Martin ME, Jensen RO, Juminaga A, Mihalcea C, Angenent LT. Carbon recovery by fermentation of CO-rich off gases - Turning steel mills into biorefineries. BIORESOURCE TECHNOLOGY 2016; 215:386-396. [PMID: 27095410 DOI: 10.1016/j.biortech.2016.03.094] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 05/08/2023]
Abstract
Technological solutions to reduce greenhouse gas (GHG) emissions from anthropogenic sources are required. Heavy industrial processes, such as steel making, contribute considerably to GHG emissions. Fermentation of carbon monoxide (CO)-rich off gases with wild-type acetogenic bacteria can be used to produce ethanol, acetate, and 2,3-butanediol, thereby, reducing the carbon footprint of heavy industries. Here, the processes for the production of ethanol from CO-rich off gases are discussed and a perspective on further routes towards an integrated biorefinery at a steel mill is given. Recent achievements in genetic engineering as well as integration of other biotechnology platforms to increase the product portfolio are summarized. Already, yields have been increased and the portfolio of products broadened. To develop a commercially viable process, however, the extraction from dilute product streams is a critical step and alternatives to distillation are discussed. Finally, another critical step is waste(water) treatment with the possibility to recover resources.
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Affiliation(s)
- Bastian Molitor
- Department of Biological and Environmental Engineering, Cornell University, Riley-Robb Hall, Ithaca, NY 14853, United States
| | - Hanno Richter
- Department of Biological and Environmental Engineering, Cornell University, Riley-Robb Hall, Ithaca, NY 14853, United States
| | - Michael E Martin
- LanzaTech, 8045 Lamon Avenue, Suite 400, Skokie, IL 60077, United States
| | - Rasmus O Jensen
- LanzaTech, 8045 Lamon Avenue, Suite 400, Skokie, IL 60077, United States
| | - Alex Juminaga
- LanzaTech, 8045 Lamon Avenue, Suite 400, Skokie, IL 60077, United States
| | | | - Largus T Angenent
- Department of Biological and Environmental Engineering, Cornell University, Riley-Robb Hall, Ithaca, NY 14853, United States.
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Liew F, Martin ME, Tappel RC, Heijstra BD, Mihalcea C, Köpke M. Gas Fermentation-A Flexible Platform for Commercial Scale Production of Low-Carbon-Fuels and Chemicals from Waste and Renewable Feedstocks. Front Microbiol 2016; 7:694. [PMID: 27242719 PMCID: PMC4862988 DOI: 10.3389/fmicb.2016.00694] [Citation(s) in RCA: 206] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 04/26/2016] [Indexed: 12/13/2022] Open
Abstract
There is an immediate need to drastically reduce the emissions associated with global fossil fuel consumption in order to limit climate change. However, carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources and currently there is no alternative source available to adequately displace them. Gas-fermenting microorganisms that fix carbon dioxide (CO2) and carbon monoxide (CO) can break this dependence as they are capable of converting gaseous carbon to fuels and chemicals. As such, the technology can utilize a wide range of feedstocks including gasified organic matter of any sort (e.g., municipal solid waste, industrial waste, biomass, and agricultural waste residues) or industrial off-gases (e.g., from steel mills or processing plants). Gas fermentation has matured to the point that large-scale production of ethanol from gas has been demonstrated by two companies. This review gives an overview of the gas fermentation process, focusing specifically on anaerobic acetogens. Applications of synthetic biology and coupling gas fermentation to additional processes are discussed in detail. Both of these strategies, demonstrated at bench-scale, have abundant potential to rapidly expand the commercial product spectrum of gas fermentation and further improve efficiencies and yields.
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Schulte MJ, Wiltgen J, Ritter J, Mooney CB, Flickinger MC. A high gas fraction, reduced power, syngas bioprocessing method demonstrated with a Clostridium ljungdahlii OTA1 paper biocomposite. Biotechnol Bioeng 2016; 113:1913-23. [PMID: 26927418 DOI: 10.1002/bit.25966] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 02/02/2016] [Accepted: 02/21/2016] [Indexed: 01/30/2023]
Abstract
We propose a novel approach to continuous bioprocessing of gases. A miniaturized, coated-paper strip, high gas fraction, biocomposite absorber has been developed using slowly shaken horizontal anaerobic tubes. Concentrated Clostridium ljungdahlii OTA1 was used as a model system. These gas absorbers demonstrate elevated CO mass transfer with low power input, reduced liquid requirements, elevated substrate consumption, and increased product secretion compared to shaken suspended cells. Concentrated OTA1 cell paste was coated by extrusion onto chromatography paper. The immobilized system shows high, constant reactivity immediately upon rehydration. Cell adhesion was by adsorption to the cellulose fibers; visualized by SEM. The C. ljungdahlii OTA1 coated paper mounted above the liquid level absorbs CO and H2 from a model syngas secreting acetate with minimal ethanol. At 100 rpm shaking speed (7.7 Wm(-3) ) the optimal cell loading is 6.5 gDCW m(-2) to maintain high CO absorbing reactivity without the cells coming off of the paper into the liquid phase. Reducing the medium volume from 10 mL to 4 mL (15% of tube volume) did not decrease CO reactivity. The reduced liquid volume increased secreted product concentration by 80%. The specific CO consumption by paper biocomposites was higher at all shaking frequencies <100 rpm than suspended cells under identical incubation conditions. At 25 rpm the biocomposite outperforms suspended cells for CO absorption by 2.5-fold, with an estimated power reduction of 97% over the power input at 100 rpm. The estimated minimum kL a for miniaturized biocomposite gas-absorbers is ∼100 h(-1) , 10 to 10(4) less power input than other syngas fermentation systems reported in the literature at similar kL a. Specific consumption rates in a biocomposite were ∼14 mmol gDCW-1 h(-1) . This work intensified CO absorption and reactivity by 14-fold to 94 mmol CO m(-2) h(-1) over previous C. ljungdahlii OTA1 work by our group. Specific acetate production rates were 23 mM h(-1) or 46 mmol m(-2) h(-1) . The specific rates and apparent kL a scaled linearly with biocomposite coating area. Biotechnol. Bioeng. 2016;113: 1913-1923. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Mark J Schulte
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Raleigh, North Carolina, 27695
| | - Jeff Wiltgen
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Raleigh, North Carolina, 27695
| | - John Ritter
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Raleigh, North Carolina, 27695
| | - Charles B Mooney
- Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina
| | - Michael C Flickinger
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Raleigh, North Carolina, 27695. .,Golden-LEAF Biomanufacturing Training and Education Center, North Carolina State University, Raleigh, North Carolina, 27695.
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