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Feng X, Kazama D, He S, Nakayama H, Hayashi T, Tokunaga T, Sato K, Kobayashi H. Enrichment of halotolerant hydrogen-oxidizing bacteria and production of high-value-added chemical hydroxyectoine using a hybrid biological-inorganic system. Front Microbiol 2023; 14:1254451. [PMID: 37711693 PMCID: PMC10497747 DOI: 10.3389/fmicb.2023.1254451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 08/15/2023] [Indexed: 09/16/2023] Open
Abstract
Hybrid biological-inorganic (HBI) systems show great promise as CO2 conversion platforms combining CO2 fixation by hydrogen-oxidizing bacteria (HOB) with water splitting. Herein, halotolerant HOB were enriched using an HBI system with a high-ionic-strength medium containing 180 mM phosphate buffer to identify new biocatalysts. The reactors were inoculated with samples from saline environments and applied with a voltage of 2.0 V. Once an increase in biomass was observed with CO2 consumption, an aliquot of the medium was transferred to a new reactor. After two successive subcultures, Achromobacter xylosoxidans strain H1_3_1 and Mycolicibacterium mageritense strain H4_3_1 were isolated from the reactor media. Genome sequencing indicated the presence of genes for aerobic hydrogen-oxidizing chemolithoautotrophy and synthesis of the compatible solute hydroxyectoine in both strains. Furthermore, both strains produced hydroxyectoine in the reactors under the high-ionic-strength condition, suggesting the potential for new HBI systems using halotolerant HOB to produce high-value-added chemicals.
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Affiliation(s)
- Xiang Feng
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Daichi Kazama
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Sijia He
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Hideki Nakayama
- Department of Environmental Science, Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan
| | - Takeshi Hayashi
- Department of Regional Studies and Humanities, Faculty of Education and Human Studies, Akita University, Akita, Japan
| | - Tomochika Tokunaga
- Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
| | - Kozo Sato
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
- Frontier Research Center for Energy and Resource, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Hajime Kobayashi
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
- Frontier Research Center for Energy and Resource, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
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Feng X, He S, Sato T, Kondo T, Uema K, Sato K, Kobayashi H. Enrichment of hydrogen-oxidizing bacteria using a hybrid biological-inorganic system. J Biosci Bioeng 2023; 135:250-257. [PMID: 36650080 DOI: 10.1016/j.jbiosc.2022.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/06/2022] [Accepted: 12/23/2022] [Indexed: 01/19/2023]
Abstract
Hybrid biological-inorganic (HBI) systems comprising inorganic water-splitting catalysts and aerobic hydrogen-oxidizing bacteria (HOB) have previously been used for CO2 conversion. In order to identify new biocatalysts for CO2 conversion, the present study used an HBI system to enrich HOB directly from environmental samples. Three sediment samples (from a brackish water pond, a beach, and a tide pool) and two activated sludge samples (from two separate sewage plants) were inoculated into HBI systems using a cobalt phosphorus (Co-P) alloy and cobalt phosphate (CoPi) as inorganic catalysts with a fixed voltage of 2.0 V. The gas composition of the reactor headspaces and electric current were monitored. An aliquot of the reactor medium was transferred to a new reactor when significant consumption of H2 and CO2 was detected. This process was repeated twice (with three reactors in operation for each sample) to enrich HOB. Increased biomass concomitant with increased H2 and CO2 consumption was observed in the third reactor, indicating enrichment of HOB. 16S rRNA gene amplicon sequencing demonstrated enrichment of sequences related to HOB (including bacteria from Mycobacterium, Hydrogenophaga, and Xanthobacter genera) over successive sub-cultures. Finally, four different HOB belonging to the Mycobacterium, Hydrogenophaga, Xanthobacter, and Acidovorax genera were isolated from reactor media, representing potential candidates as HBI system biocatalysts.
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Affiliation(s)
- Xiang Feng
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Sijia He
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Taiki Sato
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Takumi Kondo
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Koyo Uema
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kozo Sato
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Frontier Research Center for Energy and Resource (FRCER), Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Hajime Kobayashi
- Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Frontier Research Center for Energy and Resource (FRCER), Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
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