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Policastro G, Cesaro A, Fabbricino M. Valorization of Purple Phototrophic Bacteria Biomass Resulting from Photo Fermentation Aimed at Biohydrogen Production. Molecules 2024; 29:1679. [PMID: 38611957 PMCID: PMC11013808 DOI: 10.3390/molecules29071679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/03/2024] [Accepted: 04/04/2024] [Indexed: 04/14/2024] Open
Abstract
This study evaluated the feasibility of contextually producing hydrogen, microbial proteins, and polyhydroxybutyrate (PHB) using a mixed culture of purple phototrophic bacteria biomass under photo fermentative conditions. To this end, three consecutive batch tests were conducted to analyze the biomass growth curve and to explore the potential for optimizing the production process. Experimental findings indicated that inoculating reactors with microorganisms from the exponential growth phase reduced the duration of the process. Furthermore, the most effective approach for simultaneous hydrogen production and the valorization of microbial biomass was found when conducting the process during the exponential growth phase of the biomass. At this stage, achieved after 3 days of fermentation, the productivities of hydrogen, PHB, and microbial proteins were measured at 63.63 L/m3 d, 0.049 kg/m3 d, and 0.045 kg/m3 d, respectively. The biomass composition comprised a total intracellular compound percentage of 56%, with 27% representing PHB and 29% representing proteins. Under these conditions, the estimated daily revenue was maximized, amounting to 0.6 $/m3 d.
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Affiliation(s)
- Grazia Policastro
- Department of Engineering, Telematic University Pegaso, 80143 Naples, Italy;
| | - Alessandra Cesaro
- Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, 80125 Naples, Italy;
| | - Massimiliano Fabbricino
- Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, 80125 Naples, Italy;
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Evaluation of Growth and Utilization Potential of Rhodobacter sphaeroides in Reused Medium. Mol Biotechnol 2023; 65:441-445. [PMID: 35982379 DOI: 10.1007/s12033-022-00553-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 08/09/2022] [Indexed: 10/15/2022]
Abstract
Rhodobacter sphaeroides is a metabolically versatile purple non-sulfur bacteria that can produce valuable substances. As the low-cost and high-efficiency production of valuable substances is attracting attention, the reuse of the medium is emerging as a promising strategy. Therefore, in this study, the growth of R. sphaeroides was evaluated by reusing the medium of Escherichia coli and Saccharomyces cerevisiae. As a result, in the reuse of the medium in which S. cerevisiae was cultured, sufficient growth of R. sphaeroides could be confirmed, and especially, the growth of R. sphaeroides was not inhibited under aerobic conditions. Therefore, it is considered that the strategy of reusing the medium of S. cerevisiae is sufficiently feasible. Of the organic compounds investigated, R. sphaeroides grew best in succinic acid, followed by malic acid, citric acid, acetic acid, and glucose. In addition, by comparing photopigment synthesis in the reused medium, we propose the hypothesis that succinic acid may play an important role in photopigment synthesis for the first time.
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Isolation and Genomics of Futiania mangrovii gen. nov., sp. nov., a Rare and Metabolically Versatile Member in the Class Alphaproteobacteria. Microbiol Spectr 2023; 11:e0411022. [PMID: 36541777 PMCID: PMC9927469 DOI: 10.1128/spectrum.04110-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mangrove microorganisms are a major part of the coastal ecosystem and are directly associated with nutrient cycling. Despite their ecological significance, the collection of culturable mangrove microbes is limited due to difficulties in isolation and cultivation. Here, we report the isolation and genome sequence of strain FT118T, the first cultured representative of a previously uncultivated order UBA8317 within Alphaproteobacteria, based on the combined results of 16S rRNA gene similarity, phylogenomic, and average amino acid identity analyses. We propose Futianiales ord. nov. and Futianiaceae fam. nov. with Futiania as the type genus, and FT118T represents the type species with the name Futiania mangrovii gen. nov, sp. nov. The 16S rRNA gene sequence comparison reveals that this novel order is a rare member but has a ubiquitous distribution across various habitats worldwide, which is corroborated by the experimental confirmation that this isolate can physiologically adapt to a wide range of oxygen levels, temperatures, pH and salinity levels. Biochemical characterization, genomic annotation, and metatranscriptomic analysis of FT118T demonstrate that it is metabolically versatile and active in situ. Genomic analysis reveals adaptive features of Futianiales to fluctuating mangrove environments, including the presence of high- and low-affinity terminal oxidases, N-type ATPase, and the genomic capability of producing various compatible solutes and polyhydroxybutyrate, which possibly allow for the persistence of this novel order across various habitats. Collectively, these results expand the current culture collection of mangrove microorganisms, providing genomic insights of how this novel taxon adapts to fluctuating environments and the culture reference to unravel possible microbe-environment interactions. IMPORTANCE The rare biosphere constitutes an essential part of the microbial community and may drive nutrient cycling and other geochemical processes. However, the difficulty in microbial isolation and cultivation has hampered our understanding of the physiology and ecology of uncultured rare lineages. In this study, we successfully isolated a novel alphaproteobacterium, designated as FT118T, and performed a combination of phenotypic, phylogenetic, and phylogenomic analyses, confirming that this isolate represents the first cultured member of a previously uncultivated order UBA8317 within Alphaproteobacteria. It is a rare species with a ubiquitous distribution across different habitats. Genomic and metatranscriptomic analyses demonstrate that it is metabolically versatile and active in situ, suggesting its potential role in nutrient cycling despite being scarce. This work not only expands the current phylogeny of isolated Alphaproteobacteria but also provides genomic and culture reference to unravel microbial adaptation strategies in mangrove sediments and possible microbe-environment interactions.
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Esposito FP, Vecchiato V, Buonocore C, Tedesco P, Noble B, Basnett P, de Pascale D. Enhanced production of biobased, biodegradable, Poly(3-hydroxybutyrate) using an unexplored marine bacterium Pseudohalocynthiibacter aestuariivivens, isolated from highly polluted coastal environment. BIORESOURCE TECHNOLOGY 2023; 368:128287. [PMID: 36368485 DOI: 10.1016/j.biortech.2022.128287] [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: 09/26/2022] [Revised: 11/02/2022] [Accepted: 11/03/2022] [Indexed: 06/16/2023]
Abstract
The production and disposal of plastics from limited fossil reserves, has prompted research for greener and sustainable alternatives. Polyhydroxyalkanoates (PHAs) are biocompatible, biodegradable, and thermoprocessable polyester produced by microbes. PHAs found several applications but their use is limited due to high production cost and low yields. Herein, for the first time, the isolation and characterization of Pseudohalocynthiibacter aestuariivivens P96, a marine bacterium able to produce surprising amount of PHAs is reported. In the best growth condition P96 was able to reach a maximum production of 4.73 g/L, corresponding to the 87 % of total cell dry-weight. Using scanning and transmission microscopy, lab-scale fermentation, spectroscopic techniques, and genome analysis, the production of thermoprocessable polymer Polyhydroxybutyrate P(3HB), a PHAs class, endowed with mechanical and thermal properties comparable to that of petroleum-based plastics was confirmed. This study represents a milestone toward the use of this unexplored marine bacterium for P(3HB) production.
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Affiliation(s)
- Fortunato Palma Esposito
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Acton 55, 80133 Naples, Italy
| | - Vittoria Vecchiato
- Sustainable Biotechnology Research Group, School of Life Sciences, University of Westminster, London W1W6UW, United Kingdom
| | - Carmine Buonocore
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Acton 55, 80133 Naples, Italy
| | - Pietro Tedesco
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Acton 55, 80133 Naples, Italy
| | - Brendon Noble
- Sustainable Biotechnology Research Group, School of Life Sciences, University of Westminster, London W1W6UW, United Kingdom
| | - Pooja Basnett
- Sustainable Biotechnology Research Group, School of Life Sciences, University of Westminster, London W1W6UW, United Kingdom
| | - Donatella de Pascale
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Acton 55, 80133 Naples, Italy.
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Acharjee SA, Bharali P, Gogoi B, Sorhie V, Walling B. PHA-Based Bioplastic: a Potential Alternative to Address Microplastic Pollution. WATER, AIR, AND SOIL POLLUTION 2022; 234:21. [PMID: 36593989 PMCID: PMC9797907 DOI: 10.1007/s11270-022-06029-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 12/14/2022] [Indexed: 06/01/2023]
Abstract
Petroleum-derived plastics are linked to a variety of growing environmental issues throughout their lifecycle, including emission of greenhouse gases, accumulation in terrestrial and marine habitats, pollution, among others. There has been a lot of attention over the last decade in industrial and research communities in developing and producing eco-friendly polymers to deal with the current environmental issues. Bioplastics preferably are a fast-developing family of polymeric substances that are frequently promoted as substitutes to petroleum-derived plastics. Polyhydroxyalkanoates (PHAs) have a number of appealing properties that make PHAs a feasible source material for bioplastics, either as a direct replacement of petroleum-derived plastics or as a blend with elements derived from natural origin, fabricated biodegradable polymers, and/or non-biodegradable polymers. Among the most promising PHAs, polyhydroxybutyrates (PHBs) are the most well-known and have a significant potential to replace traditional plastics. These biodegradable plastics decompose faster after decomposing into carbon dioxide, water, and inorganic chemicals. Bioplastics have been extensively utilized in several sectors such as food-processing industry, medical, agriculture, automobile industry, etc. However, it is also associated with disadvantages like high cost, uneconomic feasibility, brittleness, and hydrophilic nature. A variety of tactics have been explored to improve the qualities of bioplastics, with the most prevalent being the development of gas and water barrier properties. The prime objective of this study is to review the current knowledge on PHAs and provide a brief introduction to PHAs, which have drawn attention as a possible potential alternative to conventional plastics due to their biological origin, biocompatibility, and biodegradability, thereby reducing the negative impact of microplastics in the environment. This review may help trigger further scientific interest to thoroughly research on PHAs as a sustainable option to greener bioplastics.
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Affiliation(s)
- Shiva Aley Acharjee
- Applied Environmental Microbial Biotechnology Laboratory, Department of Environmental Science, Nagaland University, Hq- Lumami, Zunheboto-798627, Nagaland, India
| | - Pranjal Bharali
- Applied Environmental Microbial Biotechnology Laboratory, Department of Environmental Science, Nagaland University, Hq- Lumami, Zunheboto-798627, Nagaland, India
| | - Bhagyudoy Gogoi
- Applied Environmental Microbial Biotechnology Laboratory, Department of Environmental Science, Nagaland University, Hq- Lumami, Zunheboto-798627, Nagaland, India
| | - Viphrezolie Sorhie
- Applied Environmental Microbial Biotechnology Laboratory, Department of Environmental Science, Nagaland University, Hq- Lumami, Zunheboto-798627, Nagaland, India
| | - Bendangtula Walling
- Applied Environmental Microbial Biotechnology Laboratory, Department of Environmental Science, Nagaland University, Hq- Lumami, Zunheboto-798627, Nagaland, India
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Lee S, Rim Lee Y, Lee WH, Youn Lee S, Moon M, Woo Park G, Min K, Lee J, Lee JS. Valorization of CO 2 to β-farnesene in Rhodobacter sphaeroides. BIORESOURCE TECHNOLOGY 2022; 363:127955. [PMID: 36115510 DOI: 10.1016/j.biortech.2022.127955] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 06/15/2023]
Abstract
The valorization of CO2 into valuable products is a sustainable strategy to help overcome the climate crisis. In particular, biological conversion is attractive as it can produce long-chain hydrocarbons such as terpenoids. This study reports the high yield of β-farnesene production from CO2 by expressing heterologous β-farnesene synthase (FS) into Rhodobacter sphaeroides. To increase the expression of FS, a strong active promoter and a ribosome binding site (RBS) were engineered. Moreover, β-farnesene production was improved further through the supply of exogenous antioxidants and additional nutrients. Finally, β-farnesene was produced from CO2 at a titer of 44.53 mg/L and yield of 234.08 mg/g, values that were correspondingly 23 times and 46 times higher than those from the initial production of β-farnesene. Altogether, the results here suggest that the autotrophic production of β-farnesene can provide a starting point for achieving a circular carbon economy.
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Affiliation(s)
- Sangmin Lee
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea
| | - Yu Rim Lee
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea; Interdisciplinary Program of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Won-Heong Lee
- Interdisciplinary Program of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Republic of Korea; Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Soo Youn Lee
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea
| | - Myounghoon Moon
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea
| | - Gwon Woo Park
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea
| | - Kyoungseon Min
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea
| | - Juah Lee
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea
| | - Jin-Suk Lee
- Gwangju Bio/Energy Research and Development Center, Korea Institute of Energy Research, Gwangju 61003, Republic of Korea.
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Simona C, Laura L, Francesco V, Marianna V, Cristina MG, Barbara T, Mauro M, Simona R. Effect of the organic loading rate on the PHA-storing microbiome in sequencing batch reactors operated with uncoupled carbon and nitrogen feeding. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 825:153995. [PMID: 35192819 DOI: 10.1016/j.scitotenv.2022.153995] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 01/28/2022] [Accepted: 02/15/2022] [Indexed: 06/14/2023]
Abstract
Over the last years, in a search for sustainable and biodegradable alternatives to petrol-based plastics, biotechnological applications turned to the potentialities of mixed microbial cultures (MMC) for producing polyhydroxyalkanoates (PHAs). Under a feast and famine regime, an uncoupled carbon (C) and nitrogen (N)-feeding strategy may be adopted by dosing the C-source at the beginning of the feast and the N-source at the beginning of the famine in order to stimulate a PHA storage response and microbial growth. Even though this strategy has been already successfully applied for the PHA production, very few information is to date available regarding the MMC operating in these systems and the influence of Organic Loading Rate (OLR) on their selection and enrichment. To fill the gap, this study investigated the effect of the OLR on the selection of PHA-accumulating microorganisms in a sequencing batch reactor (SBR) operated with an uncoupled C and N feeding strategy. The SBR cycle length was set at 12 h and four OLRs values (4.25, 8.50, 12.75 and 18 gCOD L-1 d-1) were tested by changing the concentration of the feeding solution, made of a synthetic mixture of acetic (85% of the overall COD) and propionic (15%) acids. The PHA-storage yield increased by increasing the OLR (up to 0.69 COD/COD at 12.75 gCOD L-1 d-1) but significantly decreased (0.27 COD/COD) at 18 gCOD L-1 d-1 concomitantly with a longer feast phase and a lower PHA content in the biomass at the end of the feast phase. The selective pressure induced by the applied OLRs strongly influenced the microbiome composition revealing a high content of putative PHA-storing bacteria, such as Rhodobacter, Thauera and Paracoccus, in the SBR operated at OLRs 4.25, 8.50 and 12.75 g COD L-1 d-1 (up to 97.4% of total reads) and a low content (5.4%) in the SBR at 18 g COD L-1 d-1where the predominance of genus Nitrinicola was instead observed.
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Affiliation(s)
- Crognale Simona
- Water Research Institute, National Research Council (IRSA-CNR), Monterotondo, Rome, Italy.
| | - Lorini Laura
- Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Valentino Francesco
- Department of Environmental Sciences, Informatics and Statistics, "Cà Foscari" University of Venice, Via Torino 155, 30170 Mestre-Venice, Italy
| | - Villano Marianna
- Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Marzo Gago Cristina
- Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; Department of Chemical Engineering and Food Technology, Faculty of Science, IVAGRO, University of Cádiz, Puerto Real, Spain
| | - Tonanzi Barbara
- Water Research Institute, National Research Council (IRSA-CNR), Monterotondo, Rome, Italy
| | - Majone Mauro
- Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Rossetti Simona
- Water Research Institute, National Research Council (IRSA-CNR), Monterotondo, Rome, Italy
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Lee YR, Lee WH, Lee SY, Lee J, Kim MS, Moon M, Park GW, Kim HS, Kim JI, Lee JS, Lee S. Regulation of Reactive Oxygen Species Promotes Growth and Carotenoid Production Under Autotrophic Conditions in Rhodobacter sphaeroides. Front Microbiol 2022; 13:847757. [PMID: 35295297 PMCID: PMC8920488 DOI: 10.3389/fmicb.2022.847757] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 02/07/2022] [Indexed: 11/26/2022] Open
Abstract
Industrial demand for capture and utilization using microorganisms to reduce CO2, a major cause of global warming, is significantly increasing. Rhodobacter sphaeroides is a suitable strain for the process of converting CO2 into high-value materials because it can accept CO2 and has various metabolic pathways. However, it has been mainly studied for heterotrophic growth that uses sugars and organic acids as carbon sources, not autotrophic growth. Here, we report that the regulation of reactive oxygen species is critical for growth when using CO2 as a sole carbon source in R. sphaeroides. In general, the growth rate is much slower under autotrophic conditions compared to heterotrophic conditions. To improve this, we performed random mutagenesis using N-methyl-N’-nitro-N-nitrosoguanidine (NTG). As a result, we selected the YR-1 strain with a maximum specific growth rate (μ) 1.44 day–1 in the early growth phase, which has a 110% faster growth rate compared to the wild-type. Based on the transcriptome analysis, it was confirmed that the growth was more sensitive to reactive oxygen species under autotrophic conditions. In the YR-1 mutant, the endogenous contents of H2O2 levels and oxidative damage were reduced by 33.3 and 42.7% in the cells, respectively. Furthermore, we measured that concentrations of carotenoids, which are important antioxidants. The total carotenoid is produced 9.63 g/L in the YR-1 mutant, suggesting that the production is 1.7-fold higher than wild-type. Taken together, our observations indicate that controlling ROS promotes cell growth and carotenoid production under autotrophic conditions.
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Affiliation(s)
- Yu Rim Lee
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
- Interdisciplinary Program of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea
| | - Won-Heong Lee
- Interdisciplinary Program of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, South Korea
| | - Soo Youn Lee
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
| | - Jiye Lee
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
| | - Min-Sik Kim
- Energy Resources Upcycling Research Laboratory, Korea Institute of Energy Research, Daejeon, South Korea
| | - Myounghoon Moon
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
| | - Gwon Woo Park
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
| | - Hui Su Kim
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
- Department of Advanced Chemicals and Engineering, Chonnam National University, Gwangju, South Korea
| | - Jeong-Il Kim
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, South Korea
| | - Jin-Suk Lee
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
| | - Sangmin Lee
- Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju, South Korea
- *Correspondence: Sangmin Lee,
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Modulation of Antioxidant Activity Enhances Photoautotrophic Cell Growth of Rhodobacter sphaeroides in Microbial Electrosynthesis. ENERGIES 2022. [DOI: 10.3390/en15030935] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Global warming is currently accelerating due to an increase in greenhouse gas emissions by industrialization. Microbial electrosynthesis (MES) using electroactive autotrophic microorganisms has recently been reported as a method to reduce carbon dioxide, the main culprit of greenhouse gas. However, there are still few cases of application of MES, and the molecular mechanisms are largely unknown. To investigate the growth characteristics in MES, we carried out growth tests according to reducing power sources in Rhodobacter sphaeroides. The growth rate was significantly lower when electrons were directly supplied to cells, compared to when hydrogen was supplied. Through a transcriptome analysis, we found that the expression of reactive oxygen species (ROS)-related genes was meaningfully higher in MES than in normal photoautotrophic conditions. Similarly, endogenous contents of H2O2 were higher and peroxidase activities were lower in MES. The exogenous application of ascorbic acid, a representative biological antioxidant, promotes cell growth by decreasing ROS levels, confirming the inhibitory effects of ROS on MES. Taken together, our observations suggest that reduction of ROS by increasing antioxidant activities is important for enhancing the cell growth and production of CO2-converting substances such as carotenoids in MES in R. sphaeroides
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Poly-β-Hydroxybutyrate Production by Rhodopseudomonas sp. Grown in Semi-Continuous Mode in a 4 L Photobioreactor. Symmetry (Basel) 2021. [DOI: 10.3390/sym13091609] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The synthesis of polyhydroxybutyrate (PHB) by photosynthetic non-sulfur bacteria is a potential approach for producing biodegradable plastics. In this work, acetate was used as a single carbon source to study the effect on PHB formation in Rhodopseudomonas sp. cultured in a cylindrical four-liter photobioreactor under semi-continuous mode. The cultivation process is divided into a symmetrical growth phase and a PHB accumulation phase separated temporally. The symmetrical growth phase (nutrient sufficient conditions) was followed by a sulfur-limited phase to promote PHB accumulation. The main novelty is the progressive lowering of the sulfur concentration into Rhodopseudomonas culture, which was obtained by two concomitant conditions: (1) sulfur consumption during the bacterial growth and (2) semi-continuous growth strategy. This caused a progressive lowering of the sulfur concentration into Rhodopseudomonas culturedue to the sulfur-free medium used to replace 2 L of culture (50% of the total) that was withdrawn from the photobioreactor at each dilution. The PHB content ranged from 9.26% to 15.24% of cell dry weight. At the steady state phase, the average cumulative PHB was >210 mg/L. Sulfur deficiency proved to be one of the most suitable conditions to obtain high cumulative PHB in Rhodopseudomonas culture.
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