1
|
Jureckova K, Nykrynova M, Slaninova E, Fleuriot-Blitman H, Amstutz V, Hermankova K, Bezdicek M, Mrazova K, Hrubanova K, Zinn M, Obruca S, Sedlar K. Cultivation driven transcriptomic changes in the wild-type and mutant strains of Rhodospirillum rubrum. Comput Struct Biotechnol J 2024; 23:2681-2694. [PMID: 39035834 PMCID: PMC11259993 DOI: 10.1016/j.csbj.2024.06.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 06/11/2024] [Accepted: 06/18/2024] [Indexed: 07/23/2024] Open
Abstract
Purple photosynthetic bacteria (PPB) are versatile microorganisms capable of producing various value-added chemicals, e.g., biopolymers and biofuels. They employ diverse metabolic pathways, allowing them to adapt to various growth conditions and even extreme environments. Thus, they are ideal organisms for the Next Generation Industrial Biotechnology concept of reducing the risk of contamination by using naturally robust extremophiles. Unfortunately, the potential of PPB for use in biotechnology is hampered by missing knowledge on regulations of their metabolism. Although Rhodospirillum rubrum represents a model purple bacterium studied for polyhydroxyalkanoate and hydrogen production, light/chemical energy conversion, and nitrogen fixation, little is known regarding the regulation of its metabolism at the transcriptomic level. Using RNA sequencing, we compared gene expression during the cultivation utilizing fructose and acetate as substrates in case of the wild-type strain R. rubrum DSM 467T and its knock-out mutant strain that is missing two polyhydroxyalkanoate synthases PhaC1 and PhaC2. During this first genome-wide expression study of R. rubrum, we were able to characterize cultivation-driven transcriptomic changes and to annotate non-coding elements as small RNAs.
Collapse
Affiliation(s)
- Katerina Jureckova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Marketa Nykrynova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Eva Slaninova
- Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Brno, Czech Republic
| | - Hugo Fleuriot-Blitman
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland Valais-Wallis (HES-SO Valais-Wallis), Sion, Switzerland
| | - Véronique Amstutz
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland Valais-Wallis (HES-SO Valais-Wallis), Sion, Switzerland
| | - Kristyna Hermankova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Matej Bezdicek
- Department of Internal Medicine – Haematology and Oncology, University Hospital Brno, Brno, Czech Republic
- Department of Internal Medicine – Haematology and Oncology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Katerina Mrazova
- Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Brno, Czech Republic
- Institute of Scientific Instruments of the Czech Academy of Sciences, v.v.i., Brno, Czech Republic
| | - Kamila Hrubanova
- Institute of Scientific Instruments of the Czech Academy of Sciences, v.v.i., Brno, Czech Republic
| | - Manfred Zinn
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland Valais-Wallis (HES-SO Valais-Wallis), Sion, Switzerland
| | - Stanislav Obruca
- Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Brno, Czech Republic
| | - Karel Sedlar
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| |
Collapse
|
2
|
Hernández-Herreros N, Rodríguez A, Galán B, Auxiliadora Prieto M. Boosting hydrogen production in Rhodospirillum rubrum by syngas-driven photoheterotrophic adaptive evolution. BIORESOURCE TECHNOLOGY 2024; 406:130972. [PMID: 38876276 DOI: 10.1016/j.biortech.2024.130972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2024] [Revised: 05/07/2024] [Accepted: 06/12/2024] [Indexed: 06/16/2024]
Abstract
Rhodospirillum rubrum is a photosynthetic purple non-sulphur bacterium with great potential to be used for complex waste valorisation in biotechnological applications due to its metabolic versatility. This study investigates the production of hydrogen (H2) and polyhydroxyalkanoates (PHA) by R. rubrum from syngas under photoheterotrophic conditions. An adaptive laboratory evolution strategy (ALE) has been carried out to improve the yield of the process. After 200 generations, two evolved strains were selected that showed reduced lag phase and enhanced poly-3-hydroxybutyrate (PHB) and H2 synthesis compared to the parental strain. Genomic analysis of the photo-adapted (PA) variants showed four genes with single point mutations, including the photosynthesis gene expression regulator PpsR. The proteome of the variants suggested that the adapted variants overproduced H2 due to a more efficient CO oxidation through the CO-dehydrogenase enzyme complex and confirmed that energy acquisition was enhanced through overexpression of the photosynthetic system and metal cofactors essential for pigment biosynthesis.
Collapse
Affiliation(s)
- Natalia Hernández-Herreros
- Microbial & Plant Biotechnology Department, Polymer Biotechnology Group, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain; Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy-Spanish National Research Council (SusPlast-CSIC), Madrid, Spain
| | - Alberto Rodríguez
- Microbial & Plant Biotechnology Department, Polymer Biotechnology Group, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain; Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy-Spanish National Research Council (SusPlast-CSIC), Madrid, Spain
| | - Beatriz Galán
- Microbial & Plant Biotechnology Department, Environmental Biotechnology Group, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain
| | - M Auxiliadora Prieto
- Microbial & Plant Biotechnology Department, Polymer Biotechnology Group, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain; Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy-Spanish National Research Council (SusPlast-CSIC), Madrid, Spain.
| |
Collapse
|
3
|
Tang M, Zhen X, Zhao G, Wu S, Hua W, Qiang J, Yanling C, Wang W. The metabolic pathways of carbon assimilation and polyhydroxyalkanoate production by Rhodospirillum rubrum in response to different atmospheric fermentation. PLoS One 2024; 19:e0306222. [PMID: 39046963 PMCID: PMC11268599 DOI: 10.1371/journal.pone.0306222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 06/12/2024] [Indexed: 07/27/2024] Open
Abstract
The purple nonsulfur bacteria, Rhodospirillum rubrum, is recognized as a potential strain for PHAs bioindustrial processes since they can assimilate a broad range of carbon sources, such as syngas, to allow reduction of the production costs. In this study, we comparatively analyzed the biomass and PHA formation behaviors of R. rubrum under 100% CO and 50% CO gas atmosphere and found that pure CO promoted the PHA synthesis (PHA content up to 23.3% of the CDW). Hydrogen addition facilitated the uptake and utilization rates of CO and elevated 3-HV monomers content (molar proportion of 3-HV up to 9.2% in the presence of 50% H2). To elucidate the genetic events culminating in the CO assimilation process, we performed whole transcriptome analysis of R. rubrum grown under 100% CO or 50% CO using RNA sequencing. Transcriptomic analysis indicated different CO2 assimilation strategy was triggered by the presence of H2, where the CBB played a minor role. An increase in BCAA biosynthesis related gene abundance was observed under 50% CO condition. Furthermore, we detected the α-ketoglutarate (αKG) synthase, converting fumarate to αKG linked to the αKG-derived amino acids synthesis, and series of threonine-dependent isoleucine synthesis enzymes were significantly induced. Collectively, our results suggested that those amino acid synthesis pathways represented a key way for carbon assimilation and redox potential maintenance by R. rubrum growth under syngas condition, which could partly replace the PHA production and affect its monomer composition in copolymers. Finally, a fed-batch fermentation of the R. rubrum in a 3-l bioreactor was carried out and proved H2 addition indeed increased the PHA accumulation rate, yielding 20% ww-1 PHA production within six days.
Collapse
Affiliation(s)
- Manyu Tang
- Biochemical Engineering College, Beijing Union University, Beijing, China
| | - Xin Zhen
- Biochemical Engineering College, Beijing Union University, Beijing, China
| | - Guoqiang Zhao
- Biochemical Engineering College, Beijing Union University, Beijing, China
| | - Shuang Wu
- Biochemical Engineering College, Beijing Union University, Beijing, China
- Beijing Key Laboratory of Biomass Waste Resource Utilization, Beijing, China
| | - Wei Hua
- Biochemical Engineering College, Beijing Union University, Beijing, China
- Beijing Key Laboratory of Biomass Waste Resource Utilization, Beijing, China
| | - Jingwen Qiang
- Biochemical Engineering College, Beijing Union University, Beijing, China
| | - Cheng Yanling
- Biochemical Engineering College, Beijing Union University, Beijing, China
- Beijing Key Laboratory of Biomass Waste Resource Utilization, Beijing, China
| | - Wanqing Wang
- Biochemical Engineering College, Beijing Union University, Beijing, China
- Beijing Key Laboratory of Biomass Waste Resource Utilization, Beijing, China
| |
Collapse
|
4
|
Godoy MS, Verdú I, de Miguel SR, Jiménez JD, Prieto MA. Exploring Rhodospirillum rubrum response to high doses of carbon monoxide under light and dark conditions. Appl Microbiol Biotechnol 2024; 108:258. [PMID: 38466440 DOI: 10.1007/s00253-024-13079-5] [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: 11/28/2023] [Revised: 01/14/2024] [Accepted: 02/16/2024] [Indexed: 03/13/2024]
Abstract
Environmental concerns about residues and the traditional disposal methods are driving the search for more environmentally conscious processes, such as pyrolysis and gasification. Their main final product is synthesis gas (syngas) composed of CO, CO2, H2, and methane. Syngas can be converted into various products using CO-tolerant microorganisms. Among them, Rhodospirillum rubrum is highlighted for its biotechnological potential. However, the extent to which high doses of CO affect its physiology is still opaque. For this reason, we have studied R. rubrum behavior under high levels of this gas (up to 2.5 bar), revealing a profound dependence on the presence or absence of light. In darkness, the key variable affected was the lag phase, where the highest levels of CO retarded growth to more than 20 days. Under light, R. rubrum ability to convert CO into CO2 and H2 depended on the presence of an additional carbon source, such as acetate. In those conditions where CO was completely exhausted, CO2 fixation was unblocked, leading to a diauxic growth. To enhance R. rubrum tolerance to CO in darkness, a UV-accelerated adaptive laboratory evolution (UVa-ALE) trial was conducted to isolate clones with shorter lag phases, resulting in the isolation of clones 1.4-2B and 1.7-2A. The adaptation of 1.4-2B was mainly based on mutated enzymes with a metabolic function, while 1.7-3A was mostly affected at regulatory genes, including the anti-repressor PpaA/AerR. Despite these mutations having slight effects on biomass and pigment levels, they successfully provoked a significant reduction in the lag phase (-50%). KEYPOINTS: • CO affects principally R. rubrum lag phase (darkness) and growth rate (light) • CO is converted to CO2/H2 during acetate uptake and inhibits CO2 fixation (light) • UVa-ALE clones showed a 50% reduction in the lag phase (darkness).
Collapse
Affiliation(s)
- Manuel S Godoy
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain.
- Interdisciplinary Platform for Sustainable Plastics Towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain.
| | - Irene Verdú
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain
- Present address: Drexel University, Philadelphia, Pennsylvania, USA
| | - Santiago R de Miguel
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain
- Interdisciplinary Platform for Sustainable Plastics Towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain
| | - José D Jiménez
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain
- Interdisciplinary Platform for Sustainable Plastics Towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain
| | - M Auxiliadora Prieto
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain.
- Interdisciplinary Platform for Sustainable Plastics Towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain.
| |
Collapse
|
5
|
Matallana-Surget S, Geron A, Decroo C, Wattiez R. Diel Cycle Proteomics: Illuminating Molecular Dynamics in Purple Bacteria for Optimized Biotechnological Applications. Int J Mol Sci 2024; 25:2934. [PMID: 38474181 DOI: 10.3390/ijms25052934] [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: 02/01/2024] [Revised: 02/27/2024] [Accepted: 02/28/2024] [Indexed: 03/14/2024] Open
Abstract
Circadian rhythms, characterized by approximately 24 h cycles, play a pivotal role in enabling various organisms to synchronize their biological activities with daily variations. While ubiquitous in Eukaryotes, circadian clocks remain exclusively characterized in Cyanobacteria among Prokaryotes. These rhythms are regulated by a core oscillator, which is controlled by a cluster of three genes: kaiA, kaiB, and kaiC. Interestingly, recent studies revealed rhythmic activities, potentially tied to a circadian clock, in other Prokaryotes, including purple bacteria such as Rhodospirillum rubrum, known for its applications in fuel and plastic bioproduction. However, the pivotal question of how light and dark cycles influence protein dynamics and the expression of putative circadian clock genes remains unexplored in purple non-sulfur bacteria. Unraveling the regulation of these molecular clocks holds the key to unlocking optimal conditions for harnessing the biotechnological potential of R. rubrum. Understanding how its proteome responds to different light regimes-whether under continuous light or alternating light and dark cycles-could pave the way for precisely fine-tuning bioproduction processes. Here, we report for the first time the expressed proteome of R. rubrum grown under continuous light versus light and dark cycle conditions using a shotgun proteomic analysis. In addition, we measured the impact of light regimes on the expression of four putative circadian clock genes (kaiB1, kaiB2, kaiC1, kaiC2) at the transcriptional and translational levels using RT-qPCR and targeted proteomic (MRM-MS), respectively. The data revealed significant effects of light conditions on the overall differential regulation of the proteome, particularly during the early growth stages. Notably, several proteins were found to be differentially regulated during the light or dark period, thus impacting crucial biological processes such as energy conversion pathways and the general stress response. Furthermore, our study unveiled distinct regulation of the four kai genes at both the mRNA and protein levels in response to varying light conditions. Deciphering the impact of the diel cycle on purple bacteria not only enhances our understanding of their ecology but also holds promise for optimizing their applications in biotechnology, providing valuable insights into the origin and evolution of prokaryotic clock mechanisms.
Collapse
Affiliation(s)
- Sabine Matallana-Surget
- Division of Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
| | - Augustin Geron
- Division of Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
- Proteomic and Microbiology Department, University of Mons, B-7000 Mons, Belgium
| | - Corentin Decroo
- Proteomic and Microbiology Department, University of Mons, B-7000 Mons, Belgium
| | - Ruddy Wattiez
- Proteomic and Microbiology Department, University of Mons, B-7000 Mons, Belgium
| |
Collapse
|
6
|
Qin N, Li L, Wang Z, Shi S. Microbial production of odd-chain fatty acids. Biotechnol Bioeng 2023; 120:917-931. [PMID: 36522132 DOI: 10.1002/bit.28308] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 10/11/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022]
Abstract
Odd-chain fatty acids (OcFAs) and their derivatives have attracted much attention due to their beneficial physiological effects and their potential to be alternatives to advanced fuels. However, cells naturally produce even-chain fatty acids (EcFAs) with negligible OcFAs. In the process of biosynthesis of fatty acids (FAs), the acetyl-CoA serves as the starter unit for EcFAs, and propionyl-CoA works as the starter unit for OcFAs. The lack of sufficient propionyl-CoA, the precursor, is usually regarded as the main restriction for large-scale bioproduction of OcFAs. In recent years, synthetic biology strategies have been used to modify several microorganisms to produce more propionyl-CoA that would enable an efficient biosynthesis of OcFAs. This review discusses several reported and potential metabolic pathways for propionyl-CoA biosynthesis, followed by advances in engineering several cell factories for OcFAs production. Finally, trends and challenges of synthetic biology driven OcFAs production are discussed.
Collapse
Affiliation(s)
- Ning Qin
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Lingyun Li
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Zheng Wang
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Shuobo Shi
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| |
Collapse
|
7
|
Godoy MS, de Miguel SR, Prieto MA. Aerobic-anaerobic transition boosts poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis in Rhodospirillum rubrum: the key role of carbon dioxide. Microb Cell Fact 2023; 22:47. [PMID: 36899367 PMCID: PMC9999600 DOI: 10.1186/s12934-023-02045-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 02/16/2023] [Indexed: 03/12/2023] Open
Abstract
BACKGROUND Microbially produced bioplastics are specially promising materials since they can be naturally synthesized and degraded, making its end-of-life management more amenable to the environment. A prominent example of these new materials are polyhydroxyalkanoates. These polyesters serve manly as carbon and energy storage and increase the resistance to stress. Their synthesis can also work as an electron sink for the regeneration of oxidized cofactors. In terms of biotechnological applications, the co-polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), or PHBV, has interesting biotechnological properties due to its lower stiffness and fragility compared to the homopolymer poly(3-hydroxybutyrate) (P3HB). In this work, we explored the potentiality of Rhodospirillum rubrum as a producer of this co-polymer, exploiting its metabolic versatility when grown in different aeration conditions and photoheterotrophically. RESULTS When shaken flasks experiments were carried out with limited aeration using fructose as carbon source, PHBV production was triggered reaching 29 ± 2% CDW of polymer accumulation with a 75 ± 1%mol of 3-hydroxyvalerate (3HV) (condition C2). Propionate and acetate were secreted in this condition. The synthesis of PHBV was exclusively carried out by the PHA synthase PhaC2. Interestingly, transcription of cbbM coding RuBisCO, the key enzyme of the Calvin-Benson-Bassham cycle, was similar in aerobic and microaerobic/anaerobic cultures. The maximal PHBV yield (81% CDW with 86%mol 3HV) was achieved when cells were transferred from aerobic to anaerobic conditions and controlling the CO2 concentration by adding bicarbonate to the culture. In these conditions, the cells behaved like resting cells, since polymer accumulation prevailed over residual biomass formation. In the absence of bicarbonate, cells could not adapt to an anaerobic environment in the studied lapse. CONCLUSIONS We found that two-phase growth (aerobic-anaerobic) significantly improved the previous report of PHBV production in purple nonsulfur bacteria, maximizing the polymer accumulation at the expense of other components of the biomass. The presence of CO2 is key in this process demonstrating the involvement of the Calvin-Benson-Bassham in the adaptation to changes in oxygen availability. These results stand R. rubrum as a promising producer of high-3HV-content PHBV co-polymer from fructose, a PHBV unrelated carbon source.
Collapse
Affiliation(s)
- Manuel S Godoy
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain.
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain.
| | - Santiago R de Miguel
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain
| | - M Auxiliadora Prieto
- Polymer Biotechnology Lab, Biological Research Centre Margarita Salas, Spanish National Research Council (CIB-CSIC), Madrid, Spain.
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy-CSIC (SusPlast-CSIC), Madrid, Spain.
| |
Collapse
|
8
|
Alloul A, Blansaer N, Cabecas Segura P, Wattiez R, Vlaeminck SE, Leroy B. Dehazing redox homeostasis to foster purple bacteria biotechnology. Trends Biotechnol 2023; 41:106-119. [PMID: 35843758 DOI: 10.1016/j.tibtech.2022.06.010] [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: 02/28/2022] [Revised: 06/14/2022] [Accepted: 06/17/2022] [Indexed: 12/27/2022]
Abstract
Purple non-sulfur bacteria (PNSB) show great potential for environmental and industrial biotechnology, producing microbial protein, biohydrogen, polyhydroxyalkanoates (PHAs), pigments, etc. When grown photoheterotrophically, the carbon source is typically more reduced than the PNSB biomass, which leads to a redox imbalance. To mitigate the excess of electrons, PNSB can exhibit several 'electron sinking' strategies, such as CO2 fixation, N2 fixation, and H2 and PHA production. The lack of a comprehensive (over)view of these redox strategies is hindering the implementation of PNSB for biotechnology applications. This review aims to present the state of the art of redox homeostasis in phototrophically grown PNSB, presenting known and theoretically expected strategies, and discussing them from stoichiometric, thermodynamic, metabolic, and economic points of view.
Collapse
Affiliation(s)
- Abbas Alloul
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Antwerpen, Belgium.
| | - Naïm Blansaer
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Antwerpen, Belgium
| | | | - Ruddy Wattiez
- Laboratory of Proteomics and Microbiology, University of Mons, Mons, Belgium
| | - Siegfried E Vlaeminck
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Antwerpen, Belgium
| | - Baptiste Leroy
- Laboratory of Proteomics and Microbiology, University of Mons, Mons, Belgium
| |
Collapse
|
9
|
Lacroux J, Atteia A, Brugière S, Couté Y, Vallon O, Steyer JP, van Lis R. Proteomics unveil a central role for peroxisomes in butyrate assimilation of the heterotrophic Chlorophyte alga Polytomella sp. Front Microbiol 2022; 13:1029828. [PMID: 36353459 PMCID: PMC9637915 DOI: 10.3389/fmicb.2022.1029828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Accepted: 10/05/2022] [Indexed: 09/08/2023] Open
Abstract
Volatile fatty acids found in effluents of the dark fermentation of biowastes can be used for mixotrophic growth of microalgae, improving productivity and reducing the cost of the feedstock. Microalgae can use the acetate in the effluents very well, but butyrate is poorly assimilated and can inhibit growth above 1 gC.L-1. The non-photosynthetic chlorophyte alga Polytomella sp. SAG 198.80 was found to be able to assimilate butyrate fast. To decipher the metabolic pathways implicated in butyrate assimilation, quantitative proteomics study was developed comparing Polytomella sp. cells grown on acetate and butyrate at 1 gC.L-1. After statistical analysis, a total of 1772 proteins were retained, of which 119 proteins were found to be overaccumulated on butyrate vs. only 46 on acetate, indicating that butyrate assimilation necessitates additional metabolic steps. The data show that butyrate assimilation occurs in the peroxisome via the β-oxidation pathway to produce acetyl-CoA and further tri/dicarboxylic acids in the glyoxylate cycle. Concomitantly, reactive oxygen species defense enzymes as well as the branched amino acid degradation pathway were strongly induced. Although no clear dedicated butyrate transport mechanism could be inferred, several membrane transporters induced on butyrate are identified as potential condidates. Metabolic responses correspond globally to the increased needs for central cofactors NAD, ATP and CoA, especially in the peroxisome and the cytosol.
Collapse
Affiliation(s)
| | - Ariane Atteia
- MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
| | - Sabine Brugière
- Univ Grenoble Alpes, CEA, INSERM, UMR BioSanté U1292, CNRS, CEA, Grenoble, France
| | - Yohann Couté
- Univ Grenoble Alpes, CEA, INSERM, UMR BioSanté U1292, CNRS, CEA, Grenoble, France
| | - Olivier Vallon
- Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne Université, Paris, France
| | | | | |
Collapse
|
10
|
Deane CS, da Silveira WA, Herranz R. Space omics research in Europe: Contributions, geographical distribution and ESA member state funding schemes. iScience 2022; 25:103920. [PMID: 35265808 PMCID: PMC8898910 DOI: 10.1016/j.isci.2022.103920] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The European research community, via European Space Agency (ESA) spaceflight opportunities, has significantly contributed toward our current understanding of spaceflight biology. Recent molecular biology experiments include "omic" analysis, which provides a holistic and systems level understanding of the mechanisms underlying phenotypic adaptation. Despite vast interest in, and the immense quantity of biological information gained from space omics research, the knowledge of ESA-related space omics works as a collective remains poorly defined due to the recent exponential application of omics approaches in space and the limited search capabilities of pre-existing records. Thus, a review of such contributions is necessary to clarify and promote the development of space omics among ESA and ESA state members. To address this gap, in this review, we i) identified and summarized omics works led by European researchers, ii) geographically described these omics works, and iii) highlighted potential caveats in complex funding scenarios among ESA member states.
Collapse
Affiliation(s)
- Colleen S Deane
- Department of Sport and Health Science, College of Life and Environmental Sciences, University of Exeter, Exeter EX1 2LU, UK.,Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | | | - Willian A da Silveira
- Department of Applied Biomedical Science, Faculty of Health Sciences, University of Malta, Msida MSD, 2080, Malta
| | - Raúl Herranz
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), 28040 Madrid, Spain
| |
Collapse
|
11
|
Study of the production of poly(hydroxybutyrate- co-hydroxyhexanoate) and poly(hydroxybutyrate- co-hydroxyvalerate- co-hydroxyhexanoate) in Rhodospirillum rubrum. Appl Environ Microbiol 2022; 88:e0158621. [PMID: 35080906 DOI: 10.1128/aem.01586-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Poly(hydroxybutyrate-co-hydroxyhexanoate) (P(HB-co-HHx)) and poly(hydroxybutyrate-co-hydroxyvalerate-co-hydroxyhexanoate) P(HB-co-HV-co-HHx) demonstrate interesting mechanical and thermal properties as well as excellent biocompatibility making them suitable for multiple applications and notably biomedical purposes. The production of such polymer was described in Rhodospirillum rubrum (Rs. rubrum), a purple non-sulfur bacteria in a nutrient-lacking environment where the HHx synthesis is triggered by the presence of hexanoate in the medium. However, the production of P(HB-co-HHx) under nutrient-balanced growth conditions has not been described so far in Rs. rubrum and the assimilation of hexanoate is poorly documented. In this study, we demonstrate using proteomic analysis and mutant fitness assay, that hexanoate assimilation involve β-oxidation and the ethylmalonyl-CoA (EMC) and methylbutanoyl-CoA (MBC) pathways, both being anaplerotic pathways already described in Rs. rubrum. Polyhydroxyalkanoate (PHA) production is likely to involve the de novo fatty acid synthesis pathway. Concerning the polymer composition, HB is the main component of the polymer, probably as acetyl-CoA and butyryl-CoA are intermediates of hexanoate assimilation pathways. When no essential nutrient is lacking in the medium, the synthesis of PHA seems to help maintain the redox balance of the cell. In this framework, we showed that the fixation of CO2 is required to sustain the growth. An increase in the proportion of HHx in the polymer was observed when redox stress was engendered in the cell under bicarbonate limiting growth conditions. The addition of isoleucine or valerate in the medium also increased the HHx content of the polymer and allowed the production of a terpolymer of P(HB-co-HV-co-HHx). Importance The use of purple bacteria, which can assimilate volatile fatty acids for biotechnological applications has risen since they reduce the production costs of added-value compounds such as PHA. P(HB-co-HHx) and P(HB-co-HV-co-HHx) have demonstrated interesting properties notably for biomedical application. In a nutrient-lacking environment, Rs. rubrum is known to synthesize such polymer when hexanoate is used as carbon source. However, their production in non-nutrient lacking growth conditions has not been described so far in Rs. rubrum and the assimilation of hexanoate is poorly documented. As the carbon source and its assimilation directly impact the polymer composition, we studied under non-nutrient lacking growth conditions, the assimilation path of hexanoate and PHA production in Rs. rubrum. Proteomic analysis and mutant fitness assay allowed to explain PHA production and composition. Increase in HHx content of the polymer and production of P(HB-co-HV-co-HHx) was possible using the knowledge gained on metabolism under hexanoate growth conditions.
Collapse
|
12
|
Rekhi P, Goswami M, Ramakrishna S, Debnath M. Polyhydroxyalkanoates biopolymers toward decarbonizing economy and sustainable future. Crit Rev Biotechnol 2021; 42:668-692. [PMID: 34645360 DOI: 10.1080/07388551.2021.1960265] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Polymers are synonymous with the modern way of living. However, polymers with a large carbon footprint, especially those derived from nonrenewable petrochemical sources, are increasingly perceived as detrimental to the environment and a sustainable future. Polyhydroxyalkanoate (PHA) is a microbial biopolymer and a plausible alternative for renewable sources. However, PHA in its monomeric forms has very limited applications due to its limited flexibility, tensile strength, and moldability. Herein, the life cycle of PHA molecules, from biosynthesis to commercial utilization for diverse applications is discussed. For clarity, the applications of this bioplastic biocomposite material are further segregated into two domains, namely, the industrial sector and the medical sector. The industry sectors reviewed here include food packaging, textiles, agriculture, automotive, and electronics. High-value addition of PHA for a sustainable future can be foreseen in the medical domain. Properties such as biodegradability and biocompatibility make PHA a suitable candidate for decarbonizing biomaterials during tissue repair, organ reconstruction, drug delivery, bone tissue engineering, and chemotherapeutics.
Collapse
Affiliation(s)
- Pavni Rekhi
- Department of Biosciences, Manipal University Jaipur, Jaipur, India
| | - Moushmi Goswami
- Department of Biosciences, Manipal University Jaipur, Jaipur, India
| | - Seeram Ramakrishna
- Department of Mechanical Engineering, National University of Singapore, Singapore, Singapore
| | - Mousumi Debnath
- Department of Biosciences, Manipal University Jaipur, Jaipur, India
| |
Collapse
|
13
|
Cabecas Segura P, De Meur Q, Tanghe A, Onderwater R, Dewasme L, Wattiez R, Leroy B. Effects of Mixing Volatile Fatty Acids as Carbon Sources on Rhodospirillum rubrum Carbon Metabolism and Redox Balance Mechanisms. Microorganisms 2021; 9:1996. [PMID: 34576891 PMCID: PMC8471276 DOI: 10.3390/microorganisms9091996] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 09/15/2021] [Accepted: 09/16/2021] [Indexed: 11/16/2022] Open
Abstract
Rhodospirillum rubrum has a versatile metabolism, and as such can assimilate a broad range of carbon sources, including volatile fatty acids. These carbon sources are gaining increasing interest for biotechnological processes, since they reduce the production costs for numerous value-added compounds and contribute to the development of a more circular economy. Usually, studies characterizing carbon metabolism are performed by supplying a single carbon source; however, in both environmental and engineered conditions, cells would rather grow on mixtures of volatile fatty acids (VFAs) generated via anaerobic fermentation. In this study, we show that the use of a mixture of VFAs as carbon source appears to have a synergy effect on growth phenotype. In addition, while propionate and butyrate assimilation in Rs. rubrum is known to require an excess of bicarbonate in the culture medium, mixing them reduces the requirement for bicarbonate supplementation. The fixation of CO2 is one of the main electron sinks in purple bacteria; therefore, this observation suggests an adaptation of both metabolic pathways used for the assimilation of these VFAs and redox homeostasis mechanism. Based on proteomic data, modification of the propionate assimilation pathway seems to occur with a switch from a methylmalonyl-CoA intermediate to the methylcitrate cycle. Moreover, it seems that the presence of a mixture of VFAs switches electron sinking from CO2 fixation to H2 and isoleucine production.
Collapse
Affiliation(s)
- Paloma Cabecas Segura
- Laboratory of Proteomics and Microbiology, University of Mons, 7000 Mons, Belgium; (P.C.S.); (Q.D.M.); (R.W.)
| | - Quentin De Meur
- Laboratory of Proteomics and Microbiology, University of Mons, 7000 Mons, Belgium; (P.C.S.); (Q.D.M.); (R.W.)
| | - Audrey Tanghe
- Materia Nova ASBL, Parc Initialis, Avenue Copernic 3, 7000 Mons, Belgium; (A.T.); (R.O.)
| | - Rob Onderwater
- Materia Nova ASBL, Parc Initialis, Avenue Copernic 3, 7000 Mons, Belgium; (A.T.); (R.O.)
| | - Laurent Dewasme
- Systems, Estimation, Control and Optimization Group, University of Mons, 7000 Mons, Belgium;
| | - Ruddy Wattiez
- Laboratory of Proteomics and Microbiology, University of Mons, 7000 Mons, Belgium; (P.C.S.); (Q.D.M.); (R.W.)
| | - Baptiste Leroy
- Laboratory of Proteomics and Microbiology, University of Mons, 7000 Mons, Belgium; (P.C.S.); (Q.D.M.); (R.W.)
| |
Collapse
|
14
|
Bayon-Vicente G, Marchand E, Ducrotois J, Dufrasne FE, Hallez R, Wattiez R, Leroy B. Analysis of the Involvement of the Isoleucine Biosynthesis Pathway in Photoheterotrophic Metabolism of Rhodospirillum rubrum. Front Microbiol 2021; 12:731976. [PMID: 34621257 PMCID: PMC8490811 DOI: 10.3389/fmicb.2021.731976] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/26/2021] [Indexed: 12/05/2022] Open
Abstract
Purple non-sulfur bacteria (PNSB) are recognized as a highly versatile group of bacteria that assimilate a broad range of carbon sources. Growing heterotrophically, PNSB such as Rhodospirillum rubrum (Rs. rubrum) generate reduced equivalents that are used for biomass production. However, under photoheterotrophic conditions, more reduced electron carriers than required to produce biomass are generated. The excess of reduced equivalents still needs to be oxidized for the metabolism to optimally operate. These metabolic reactions are known as electron sinks. Most PNSB rely on the CO2-fixing Calvin cycle and H2 production to oxidize these reduced equivalents. In addition to these well-described electron sinks, the involvement of some pathways, such as polyhydroxyalkanoate (PHA) biosynthesis, in redox poise is still controversial and requires further studies. Among them, isoleucine biosynthesis has been recently highlighted as one of these potential pathways. Here, we explore the role of isoleucine biosynthesis in Rs. rubrum. Our results demonstrate that the isoleucine content is higher under illuminated conditions and that submitting Rs. rubrum to light stress further increases this phenomenon. Moreover, we explore the production of (p)ppGpp in Rs. rubrum and its potential link with light stress. We further demonstrate that a fully functional isoleucine biosynthesis pathway could be an important feature for the onset of Rs. rubrum growth under photoheterotrophic conditions even in the presence of an exogenous isoleucine source. Altogether, our data suggest that isoleucine biosynthesis could play a key role in redox homeostasis.
Collapse
Affiliation(s)
- Guillaume Bayon-Vicente
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Elie Marchand
- Bacterial Cell Cycle & Development (BCcD), Biology of Microorganisms Research Unit (URBM), Namur Research Institute for Life Science (NARILIS), University of Namur, Namur, Belgium
| | - Jeson Ducrotois
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - François E. Dufrasne
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Regis Hallez
- Bacterial Cell Cycle & Development (BCcD), Biology of Microorganisms Research Unit (URBM), Namur Research Institute for Life Science (NARILIS), University of Namur, Namur, Belgium
- Namur Research College (NARC), University of Namur, Namur, Belgium
- WELBIO, University of Namur, Namur, Belgium
| | - Ruddy Wattiez
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Baptiste Leroy
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| |
Collapse
|
15
|
Rodríguez A, Hernández-Herreros N, García JL, Auxiliadora Prieto M. Enhancement of biohydrogen production rate in Rhodospirillum rubrum by a dynamic CO-feeding strategy using dark fermentation. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:168. [PMID: 34362414 PMCID: PMC8343937 DOI: 10.1186/s13068-021-02017-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 07/24/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND Rhodospirillum rubrum is a purple non-sulphur bacterium that produces H2 by photofermentation of several organic compounds or by water gas-shift reaction during CO fermentation. Successful strategies for both processes have been developed in light-dependent systems. This work explores a dark fermentation bioprocess for H2 production from water using CO as the electron donor. RESULTS The study of the influence of the stirring and the initial CO partial pressure (pCO) demonstrated that the process was inhibited at pCO of 1.00 atm. Optimal pCO value was established in 0.60 atm. CO dose adaptation to bacterial growth in fed-batch fermentations increased the global rate of H2 production, yielding 27.2 mmol H2 l-1 h-1 and reduced by 50% the operation time. A kinetic model was proposed to describe the evolution of the molecular species involved in gas and liquid phases in a wide range of pCO conditions from 0.10 to 1.00 atm. CONCLUSIONS Dark fermentation in R. rubrum expands the ways to produce biohydrogen from CO. This work optimizes this bioprocess at lab-bioreactor scale studying the influence of the stirring speed, the initial CO partial pressure and the operation in batch and fed-batch regimes. Dynamic CO supply adapted to the biomass growth enhances the productivity reached in darkness by other strategies described in the literature, being similar to that obtained under light continuous syngas fermentations. The kinetic model proposed describes all the conditions tested.
Collapse
Affiliation(s)
- Alberto Rodríguez
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy‐of the Spanish National Research Council (SusPlast‐CSIC), Madrid, Spain
- Polymer Biotechnology Group, Department of Plant and Microbial Biotechnology, Biological Research Center, Margarita Salas”-CSIC, 28040 Madrid, Spain
| | - Natalia Hernández-Herreros
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy‐of the Spanish National Research Council (SusPlast‐CSIC), Madrid, Spain
- Polymer Biotechnology Group, Department of Plant and Microbial Biotechnology, Biological Research Center, Margarita Salas”-CSIC, 28040 Madrid, Spain
| | - José L. García
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy‐of the Spanish National Research Council (SusPlast‐CSIC), Madrid, Spain
- Environmental Biotechnology Group, Department of Plant and Microbial Biotechnology, Biological Research Center, Margarita Salas”-CSIC 28040, Madrid, Spain
| | - M. Auxiliadora Prieto
- Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy‐of the Spanish National Research Council (SusPlast‐CSIC), Madrid, Spain
- Polymer Biotechnology Group, Department of Plant and Microbial Biotechnology, Biological Research Center, Margarita Salas”-CSIC, 28040 Madrid, Spain
| |
Collapse
|
16
|
Petushkova E, Mayorova E, Tsygankov A. TCA Cycle Replenishing Pathways in Photosynthetic Purple Non-Sulfur Bacteria Growing with Acetate. Life (Basel) 2021; 11:711. [PMID: 34357087 PMCID: PMC8307300 DOI: 10.3390/life11070711] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 06/27/2021] [Accepted: 07/14/2021] [Indexed: 11/23/2022] Open
Abstract
Purple non-sulfur bacteria (PNSB) are anoxygenic photosynthetic bacteria harnessing simple organic acids as electron donors. PNSB produce a-aminolevulinic acid, polyhydroxyalcanoates, bacteriochlorophylls a and b, ubiquinones, and other valuable compounds. They are highly promising producers of molecular hydrogen. PNSB can be cultivated in organic waste waters, such as wastes after fermentation. In most cases, wastes mainly contain acetic acid. Therefore, understanding the anaplerotic pathways in PNSB is crucial for their potential application as producers of biofuels. The present review addresses the recent data on presence and diversity of anaplerotic pathways in PNSB and describes different classifications of these pathways.
Collapse
Affiliation(s)
- Ekaterina Petushkova
- Pushchino Scientific Center for Biological Research, Institute of Basic Biological Problems Russian Academy of Sciences, 2, Institutskaya Str, 142290 Pushchino, Moscow Region, Russia; (E.P.); (E.M.)
| | - Ekaterina Mayorova
- Pushchino Scientific Center for Biological Research, Institute of Basic Biological Problems Russian Academy of Sciences, 2, Institutskaya Str, 142290 Pushchino, Moscow Region, Russia; (E.P.); (E.M.)
- Pushchino State Institute of Natural Science, The Federal State Budget Educational Institution of Higher Education, 3, Prospekt Nauki, 142290 Pushchino, Moscow Region, Russia
| | - Anatoly Tsygankov
- Pushchino Scientific Center for Biological Research, Institute of Basic Biological Problems Russian Academy of Sciences, 2, Institutskaya Str, 142290 Pushchino, Moscow Region, Russia; (E.P.); (E.M.)
| |
Collapse
|
17
|
Bayon-Vicente G, Zarbo S, Deutschbauer A, Wattiez R, Leroy B. Photoheterotrophic Assimilation of Valerate and Associated Polyhydroxyalkanoate Production by Rhodospirillum rubrum. Appl Environ Microbiol 2020; 86:e00901-20. [PMID: 32651203 PMCID: PMC7480388 DOI: 10.1128/aem.00901-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/02/2020] [Indexed: 02/06/2023] Open
Abstract
Purple nonsulfur bacteria are increasingly recognized for industrial applications in bioplastics, pigment, and biomass production. In order to optimize the yield of future biotechnological processes, the assimilation of different carbon sources by Rhodospirillum rubrum has to be understood. As they are released from several fermentation processes, volatile fatty acids (VFAs) represent a promising carbon source in the development of circular industrial applications. To obtain an exhaustive characterization of the photoheterotrophic metabolism of R. rubrum in the presence of valerate, we combined phenotypic, proteomic, and genomic approaches. We obtained evidence that valerate is cleaved into acetyl coenzyme A (acetyl-CoA) and propionyl-CoA and depends on the presence of bicarbonate ions. Genomic and enzyme inhibition data showed that a functional methylmalonyl-CoA pathway is essential. Our proteomic data showed that the photoheterotrophic assimilation of valerate induces an intracellular redox stress which is accompanied by an increased abundance of phasins (the main proteins present in polyhydroxyalkanoate [PHA] granules). Finally, we observed a significant increase in the production of the copolymer P(HB-co-HV), accounting for a very high (>80%) percentage of HV monomer. Moreover, an increase in the PHA content was obtained when bicarbonate ions were progressively added to the medium. The experimental conditions used in this study suggest that the redox imbalance is responsible for PHA production. These findings also reinforce the idea that purple nonsulfur bacteria are suitable for PHA production through a strategy other than the well-known feast-and-famine process.IMPORTANCE The use and the littering of plastics represent major issues that humanity has to face. Polyhydroxyalkanoates (PHAs) are good candidates for the replacement of oil-based plastics, as they exhibit comparable physicochemical properties but are biobased and biodegradable. However, the current industrial production of PHAs is curbed by the production costs, which are mainly linked to the carbon source. Volatile fatty acids issued from the fermentation processes constitute interesting carbon sources, since they are inexpensive and readily available. Among them, valerate is gaining interest regarding the ability of many bacteria to produce a copolymer of PHAs. Here, we describe the photoheterotrophic assimilation of valerate by Rhodospirillum rubrum, a purple nonsulfur bacterium mainly known for its metabolic versatility. Using a knowledge-based optimization process, we present a new strategy for the improvement of PHA production, paving the way for the use of R. rubrum in industrial processes.
Collapse
Affiliation(s)
- Guillaume Bayon-Vicente
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Sarah Zarbo
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Adam Deutschbauer
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Ruddy Wattiez
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Baptiste Leroy
- Laboratory of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Mons, Belgium
| |
Collapse
|