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Ranaivoarisoa TO, Bai W, Karthikeyan R, Steele H, Silberman M, Olabode J, Conners E, Gallagher B, Bose A. Overexpression of RuBisCO form I and II genes in Rhodopseudomonas palustris TIE-1 augments polyhydroxyalkanoate production heterotrophically and autotrophically. Appl Environ Microbiol 2024; 90:e0143824. [PMID: 39162566 PMCID: PMC11409669 DOI: 10.1128/aem.01438-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Accepted: 07/30/2024] [Indexed: 08/21/2024] Open
Abstract
With the rising demand for sustainable renewable resources, microorganisms capable of producing bioproducts such as bioplastics are attractive. While many bioproduction systems are well-studied in model organisms, investigating non-model organisms is essential to expand the field and utilize metabolically versatile strains. This investigation centers on Rhodopseudomonas palustris TIE-1, a purple non-sulfur bacterium capable of producing bioplastics. To increase bioplastic production, genes encoding the putative regulatory protein PhaR and the depolymerase PhaZ of the polyhydroxyalkanoate (PHA) biosynthesis pathway were deleted. Genes associated with pathways that might compete with PHA production, specifically those linked to glycogen production and nitrogen fixation, were deleted. Additionally, RuBisCO form I and II genes were integrated into TIE-1's genome by a phage integration system, developed in this study. Our results show that deletion of phaR increases PHA production when TIE-1 is grown photoheterotrophically with butyrate and ammonium chloride (NH4Cl). Mutants unable to produce glycogen or fix nitrogen show increased PHA production under photoautotrophic growth with hydrogen and NH4Cl. The most significant increase in PHA production was observed when RuBisCO form I and form I & II genes were overexpressed, five times under photoheterotrophy with butyrate, two times with hydrogen and NH4Cl, and two times under photoelectrotrophic growth with N2 . In summary, inserting copies of RuBisCO genes into the TIE-1 genome is a more effective strategy than deleting competing pathways to increase PHA production in TIE-1. The successful use of the phage integration system opens numerous opportunities for synthetic biology in TIE-1.IMPORTANCEOur planet has been burdened by pollution resulting from the extensive use of petroleum-derived plastics for the last few decades. Since the discovery of biodegradable plastic alternatives, concerted efforts have been made to enhance their bioproduction. The versatile microorganism Rhodopseudomonas palustris TIE-1 (TIE-1) stands out as a promising candidate for bioplastic synthesis, owing to its ability to use multiple electron sources, fix the greenhouse gas CO2, and use light as an energy source. Two categories of strains were meticulously designed from the TIE-1 wild-type to augment the production of polyhydroxyalkanoate (PHA), one such bioplastic produced. The first group includes mutants carrying a deletion of the phaR or phaZ genes in the PHA pathway, and those lacking potential competitive carbon and energy sinks to the PHA pathway (namely, glycogen biosynthesis and nitrogen fixation). The second group comprises TIE-1 strains that overexpress RuBisCO form I or form I & II genes inserted via a phage integration system. By studying numerous metabolic mutants and overexpression strains, we conclude that genetic modifications in the environmental microbe TIE-1 can improve PHA production. When combined with other approaches (such as reactor design, use of microbial consortia, and different feedstocks), genetic and metabolic manipulations of purple nonsulfur bacteria like TIE-1 are essential for replacing petroleum-derived plastics with biodegradable plastics like PHA.
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Affiliation(s)
| | - Wei Bai
- LifeFoundry, San Jose, California, USA
| | | | - Hope Steele
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Miriam Silberman
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jennifer Olabode
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Eric Conners
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Brian Gallagher
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Arpita Bose
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
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Boucher DG, Carroll E, Nguyen ZA, Jadhav RG, Simoska O, Beaver K, Minteer SD. Bioelectrocatalytic Synthesis: Concepts and Applications. Angew Chem Int Ed Engl 2023; 62:e202307780. [PMID: 37428529 DOI: 10.1002/anie.202307780] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/08/2023] [Accepted: 07/10/2023] [Indexed: 07/11/2023]
Abstract
Bioelectrocatalytic synthesis is the conversion of electrical energy into value-added products using biocatalysts. These methods merge the specificity and selectivity of biocatalysis and energy-related electrocatalysis to address challenges in the sustainable synthesis of pharmaceuticals, commodity chemicals, fuels, feedstocks and fertilizers. However, the specialized experimental setups and domain knowledge for bioelectrocatalysis pose a significant barrier to adoption. This review introduces key concepts of bioelectrosynthetic systems. We provide a tutorial on the methods of biocatalyst utilization, the setup of bioelectrosynthetic cells, and the analytical methods for assessing bioelectrocatalysts. Key applications of bioelectrosynthesis in ammonia production and small-molecule synthesis are outlined for both enzymatic and microbial systems. This review serves as a necessary introduction and resource for the non-specialist interested in bioelectrosynthetic research.
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Affiliation(s)
- Dylan G Boucher
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Emily Carroll
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Zachary A Nguyen
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Rohit G Jadhav
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Olja Simoska
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
| | - Kevin Beaver
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Shelley D Minteer
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
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3
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Huang C, Chen Y, Cheng S, Li M, Wang L, Cheng M, Li F, Cao Y, Song H. Enhanced acetate utilization for value-added chemicals production in Yarrowia lipolytica by integration of metabolic engineering and microbial electrosynthesis. Biotechnol Bioeng 2023; 120:3013-3024. [PMID: 37306471 DOI: 10.1002/bit.28465] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 05/19/2023] [Accepted: 05/31/2023] [Indexed: 06/13/2023]
Abstract
The limited supply of reducing power restricts the efficient utilization of acetate in Yarrowia lipolytica. Here, microbial electrosynthesis (MES) system, enabling direct conversion of inward electrons to NAD(P)H, was used to improve the production of fatty alcohols from acetate based on pathway engineering. First, the conversion efficiency of acetate to acetyl-CoA was reinforced by heterogenous expression of ackA-pta genes. Second, a small amount of glucose was used as cosubstrate to activate the pentose phosphate pathway and promote intracellular reducing cofactors synthesis. Third, through the employment of MES system, the final fatty alcohols production of the engineered strain YLFL-11 reached 83.8 mg/g dry cell weight (DCW), which was 6.17-fold higher than the initial production of YLFL-2 in shake flask. Furthermore, these strategies were also applied for the elevation of lupeol and betulinic acid synthesis from acetate in Y. lipolytica, demonstrating that our work provides a practical solution for cofactor supply and the assimilation of inferior carbon sources.
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Affiliation(s)
- Congcong Huang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Yaru Chen
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Shuai Cheng
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Mengxu Li
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Luxin Wang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Meijie Cheng
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Feng Li
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Yingxiu Cao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
| | - Hao Song
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
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Khan A, Wang W, Altaf AR, Shaukat S, Zhang HJ, Rehman AU, Jun Z, Peng L. Facial Synthesis, Stability, and Interaction of Ti 3C 2T x@PC Composites for High-Performance Biocathode Microbial Electrosynthesis Systems. ACS OMEGA 2023; 8:29949-29958. [PMID: 38174107 PMCID: PMC10763723 DOI: 10.1021/acsomega.2c08163] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 05/05/2023] [Indexed: 01/05/2024]
Abstract
Developing high-performance biocathodes remain one of the most challenging aspects of the microbial electrosynthesis (MES) system and the primary factor limiting its output. Herein, a hollow porous carbon (PC) fabricated with MXenes coated over an electrode was developed for MES systems to facilitate the direct delivery of CO2 to microorganisms colonized. The result highlighted that MXene@PC (Ti3C2Tx@PC) has a surface area of 434 m2/g. The Ti3C2Tx@PC MES cycle shows that in cycle 4 and cycle 5, the values are -309.2 and -352.3. Cyclic voltammetry showed that the coated electrode current response (mA) increased from -4.5 to -20.2. The substantial redox peaks of Ti3C2Tx@PC biofilms are displayed at -741, -516, and -427 mV vs Ag/AgCl, suggesting an enhanced electron transfer owing to the Ti3C2Tx@PC complex coating. Additionally, more active sites enhanced mass transfer and microbial development, resulting in a 46% rise in butyrate compared to the uncoated control. These findings demonstrate the value of PC modification as a method for MES-based product selection.
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Affiliation(s)
- Ahsan
Riaz Khan
- Department
of Interventional and Vascular Surgery, Shanghai Tenth People’s
Hospital, Tongji University School of Medicine, Shanghai 200072, China
- National
United Engineering Laboratory for Biomedical Material Modification, Branden Industrial Park, Qihe Economic & Development
Zone, Dezhou City, Shandong 251100, China
| | - Weiming Wang
- The
Affiliated Changsha Central Hospital, Department of Oncology, Hengyang
Medical School, University of South China, Changsha 410008, China
| | - Adnan Raza Altaf
- School
of Engineering, Huazhong Agricultural University, Wuhan 430070, China
| | - Shumaila Shaukat
- College
of Chemistry and Materials Science, Northwest
University, Xi’an 710069, China
| | - Hai-Jun Zhang
- Department
of Interventional and Vascular Surgery, Shanghai Tenth People’s
Hospital, Tongji University School of Medicine, Shanghai 200072, China
- National
United Engineering Laboratory for Biomedical Material Modification, Branden Industrial Park, Qihe Economic & Development
Zone, Dezhou City, Shandong 251100, China
| | - Ata Ur Rehman
- College
of Chemistry and Materials Science, Northwest
University, Xi’an 710069, China
| | - Zhang Jun
- Research
Center for Translational Medicine, Shanghai East Hospital, School
of Medicine, Tongji University, Shanghai 200092, China
- Shanghai
Institute of Stem Cell Research and Clinical Translation, Shanghai 200020, China
| | - Luogen Peng
- The
Affiliated Changsha Central Hospital, Department of Oncology, Hengyang
Medical School, University of South China, Changsha 410008, China
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Brown B, Wilkins M, Saha R. Rhodopseudomonas palustris: A biotechnology chassis. Biotechnol Adv 2022; 60:108001. [PMID: 35680002 DOI: 10.1016/j.biotechadv.2022.108001] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 05/18/2022] [Accepted: 06/01/2022] [Indexed: 11/26/2022]
Abstract
Rhodopseudomonas palustris is an attractive option for biotechnical applications and industrial engineering due to its metabolic versatility and its ability to catabolize a wide variety of feedstocks and convert them to several high-value products. Given its adaptable metabolism, R. palustris has been studied and applied in an extensive variety of applications such as examining metabolic tradeoffs for environmental perturbations, biodegradation of aromatic compounds, environmental remediation, biofuel production, agricultural biostimulation, and bioelectricity production. This review provides a holistic summary of the commercial applications for R. palustris as a biotechnology chassis and suggests future perspectives for research and engineering.
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Affiliation(s)
- Brandi Brown
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Mark Wilkins
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA; Industrial Agricultural Products Center, University of Nebraska-Lincoln, Lincoln, NE 68583, USA; Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Rajib Saha
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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6
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Using nanomaterials to increase the efficiency of chemical production in microbial cell factories: A comprehensive review. Biotechnol Adv 2022; 59:107982. [DOI: 10.1016/j.biotechadv.2022.107982] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 04/25/2022] [Accepted: 05/10/2022] [Indexed: 12/24/2022]
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7
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Conners EM, Rengasamy K, Bose A. "Electroactive biofilms: how microbial electron transfer enables bioelectrochemical applications". J Ind Microbiol Biotechnol 2022; 49:6563884. [PMID: 35381088 PMCID: PMC9338886 DOI: 10.1093/jimb/kuac012] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 03/30/2022] [Indexed: 11/22/2022]
Abstract
Microbial biofilms are ubiquitous. In marine and freshwater ecosystems, microbe–mineral interactions sustain biogeochemical cycles, while biofilms found on plants and animals can range from pathogens to commensals. Moreover, biofouling and biocorrosion represent significant challenges to industry. Bioprocessing is an opportunity to take advantage of biofilms and harness their utility as a chassis for biocommodity production. Electrochemical bioreactors have numerous potential applications, including wastewater treatment and commodity production. The literature examining these applications has demonstrated that the cell–surface interface is vital to facilitating these processes. Therefore, it is necessary to understand the state of knowledge regarding biofilms’ role in bioprocessing. This mini-review discusses bacterial biofilm formation, cell–surface redox interactions, and the role of microbial electron transfer in bioprocesses. It also highlights some current goals and challenges with respect to microbe-mediated bioprocessing and future perspectives.
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Affiliation(s)
- Eric M Conners
- Department of Biology. One Brookings Drive, Washington University in St. Louis, Missouri, 63105, USA
| | - Karthikeyan Rengasamy
- Department of Biology. One Brookings Drive, Washington University in St. Louis, Missouri, 63105, USA
| | - Arpita Bose
- Department of Biology. One Brookings Drive, Washington University in St. Louis, Missouri, 63105, USA
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8
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Deng X, Luo D, Okamoto A. Defined and unknown roles of conductive nanoparticles for the enhancement of microbial current generation: A review. BIORESOURCE TECHNOLOGY 2022; 350:126844. [PMID: 35158034 DOI: 10.1016/j.biortech.2022.126844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 02/06/2022] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
The ability of various bacteria to make use of solid substrates through extracellular electron transfer (EET) or extracellular electron uptake (EEU) has enabled the development of valuable biotechnologies such as microbial fuel cells (MFCs) and microbial electrosynthesis (MES). It is common practice to use metallic and semiconductive nanoparticles (NPs) for microbial current enhancement. However, the effect of NPs is highly variable between systems, and there is no clear guideline for effectively increasing the current generation. In the present review, the proposed mechanisms for enhancing current production in MFCs and MES are summarized, and the critical factors for NPs to enhance microbial current generation are discussed. Implications for microbially induced iron corrosion, where iron sulfide NPs are proposed to enhance the rate of EEU, photochemically driven MES, and several future research directions to further enhance microbial current generation, are also discussed.
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Affiliation(s)
- Xiao Deng
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Dan Luo
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 13 West 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
| | - Akihiro Okamoto
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 13 West 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan.
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9
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Liao X, Pan Q, Tian X, Wu X, Zhao F. Proteomic analysis of the electron uptake pathway of Rhodopseudomonas palustris CGA009 under different cathodic potentials. Process Biochem 2022. [DOI: 10.1016/j.procbio.2022.01.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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10
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Harnessing electrical-to-biochemical conversion for microbial synthesis. Curr Opin Biotechnol 2022; 75:102687. [PMID: 35104718 DOI: 10.1016/j.copbio.2022.102687] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/18/2021] [Accepted: 01/10/2022] [Indexed: 11/23/2022]
Abstract
Electrical-to-biochemical conversion (E2BC) drives cell metabolism for biosynthesis and has become a promising way to realize green biomanufacturing. This review discusses the following aspects: 1. the natural E2BC processes and their underlying E2BC mechanism; 2. development of artificial E2BC for tunable microbial electrosynthesis; 3. design of electrobiochemical systems using self-powered, light-assisted, and nano-biohybrid approaches; 4. synthetic biology methods for efficient microbial electrosynthesis. This review also compares E2BC with electrocatalysis-biochemical conversion (EC2BC), as both strategies may lead to future carbon negative green biomanufacturing.
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Chen LF, Yu H, Zhang J, Qin HY. A short review of graphene in the microbial electrosynthesis of biochemicals from carbon dioxide. RSC Adv 2022; 12:22770-22782. [PMID: 36105988 PMCID: PMC9376761 DOI: 10.1039/d2ra02038f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 07/22/2022] [Indexed: 11/21/2022] Open
Abstract
Microbial electrosynthesis (MES) is a potential energy transformation technology for the reduction of the greenhouse gas carbon oxide (CO2) into commercial chemicals.
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Affiliation(s)
- L. F. Chen
- New Energy Materials Research Center, College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
| | - H. Yu
- New Energy Materials Research Center, College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
| | - J. Zhang
- New Energy Materials Research Center, College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
| | - H. Y. Qin
- New Energy Materials Research Center, College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
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12
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Bai W, Ranaivoarisoa TO, Singh R, Rengasamy K, Bose A. n-Butanol production by Rhodopseudomonas palustris TIE-1. Commun Biol 2021; 4:1257. [PMID: 34732832 PMCID: PMC8566592 DOI: 10.1038/s42003-021-02781-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 10/06/2021] [Indexed: 11/09/2022] Open
Abstract
Anthropogenic carbon dioxide (CO2) release in the atmosphere from fossil fuel combustion has inspired scientists to study CO2 to biofuel conversion. Oxygenic phototrophs such as cyanobacteria have been used to produce biofuels using CO2. However, oxygen generation during oxygenic photosynthesis adversely affects biofuel production efficiency. To produce n-butanol (biofuel) from CO2, here we introduce an n-butanol biosynthesis pathway into an anoxygenic (non-oxygen evolving) photoautotroph, Rhodopseudomonas palustris TIE-1 (TIE-1). Using different carbon, nitrogen, and electron sources, we achieve n-butanol production in wild-type TIE-1 and mutants lacking electron-consuming (nitrogen-fixing) or acetyl-CoA-consuming (polyhydroxybutyrate and glycogen synthesis) pathways. The mutant lacking the nitrogen-fixing pathway produce the highest n-butanol. Coupled with novel hybrid bioelectrochemical platforms, this mutant produces n-butanol using CO2, solar panel-generated electricity, and light with high electrical energy conversion efficiency. Overall, this approach showcases TIE-1 as an attractive microbial chassis for carbon-neutral n-butanol bioproduction using sustainable, renewable, and abundant resources.
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Affiliation(s)
- Wei Bai
- grid.4367.60000 0001 2355 7002Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO USA
| | - Tahina Onina Ranaivoarisoa
- grid.4367.60000 0001 2355 7002Department of Biology, Washington University in St. Louis, St. Louis, MO USA
| | - Rajesh Singh
- grid.4367.60000 0001 2355 7002Department of Biology, Washington University in St. Louis, St. Louis, MO USA
| | - Karthikeyan Rengasamy
- grid.4367.60000 0001 2355 7002Department of Biology, Washington University in St. Louis, St. Louis, MO USA
| | - Arpita Bose
- grid.4367.60000 0001 2355 7002Department of Biology, Washington University in St. Louis, St. Louis, MO USA
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Response of Methanogen Communities to the Elevation of Cathode Potentials in Bioelectrochemical Reactors Amended with Magnetite. Appl Environ Microbiol 2021; 87:e0148821. [PMID: 34432490 DOI: 10.1128/aem.01488-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Electromethanogenesis refers to the process whereby methanogens utilize current for the reduction of CO2 to CH4. Setting low cathode potentials is essential for this process. In this study, we tested if magnetite, an iron oxide mineral widespread in the environment, can facilitate the adaptation of methanogen communities to the elevation of cathode potentials in electrochemical reactors. Two-chamber electrochemical reactors were constructed with inoculants obtained from paddy field soil. We elevated cathode potentials stepwise from the initial -0.6 V versus the standard hydrogen electrode (SHE) to -0.5 V and then to -0.4 V over the 130 days of acclimation. Only weak current consumption and CH4 production were observed in the bioreactors without magnetite. However, significant current consumption and CH4 production were recorded in the magnetite bioreactors. The robustness of electroactivity of the magnetite bioreactors was not affected by the elevation of cathode potentials from -0.6 V to -0.4 V. However, the current consumption and CH4 production were halted in the bioreactors without magnetite when the cathode potentials were elevated to -0.4 V. Methanogens related to Methanospirillum were enriched on the cathode surfaces of magnetite bioreactors at -0.4 V, while Methanosarcina relatively dominated in the bioreactors without magnetite. Methanobacterium also increased in the magnetite bioreactors but stayed off electrodes at -0.4 V. Apparently, the magnetite greatly facilitates the development of biocathodes, and it appears that with the aid of magnetite, Methanospirillum spp. can adapt to the high cathode potentials, performing efficient electromethanogenesis. IMPORTANCE Converting CO2 to CH4 through bioelectrochemistry is a promising approach to the development of green energy biotechnology. This process, however, requires low cathode potentials, which entails a cost. In this study, we tested if magnetite, a conductive iron mineral, can facilitate the adaptation of methanogens to the elevation of cathode potentials. In two-chamber reactors constructed by using inoculants obtained from paddy field soil, biocathodes developed robustly in the presence of magnetite, whereas only weak activities in CH4 production and current consumption were observed in the bioreactors without magnetite. The elevation of cathode potentials did not affect the robustness of electroactivity of the magnetite bioreactors over the 130 days of acclimation. Methanospirillum strains were identified as the key methanogens associated with the cathode surfaces during the operation at high potentials. The findings reported in this study shed new light on the adaptation of methanogen communities to the elevated cathode potentials in the presence of magnetite.
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