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Hernández-Herreros N, Rivero-Buceta V, Pardo I, Prieto MA. Production of poly(3-hydroxybutyrate)/poly(lactic acid) from industrial wastewater by wild-type Cupriavidus necator H16. WATER RESEARCH 2024; 249:120892. [PMID: 38007895 DOI: 10.1016/j.watres.2023.120892] [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: 03/15/2023] [Revised: 11/13/2023] [Accepted: 11/16/2023] [Indexed: 11/28/2023]
Abstract
The massive production of urban and industrial wastes has created a clear need for alternative waste management processes. One of the more promising strategies is to use waste as raw material for the production of biopolymers such as polyhydroxyalkanoates (PHAs). In this work, a lactate-enriched stream obtained by anaerobic digestion (AD) of wastewater (WW) from a candy production plant was used as a feedstock for PHA production in wild-type Cupriavidus necator H16. Unexpectedly, we observed the accumulation of poly(3-hydroxybutyrate)/poly(lactic acid) (P(3HB)/PLA), suggesting that the non-engineered strain already possesses the metabolic potential to produce these polymers of interest. The systematic study of factors, such as incubation time, nitrogen and lactate concentration, influencing the synthesis of P(3HB)/PLA allowed the production of a panel of polymers in a resting cell system with tailored lactic acid (LA) content according to the GC-MS of the biomass. Further biomass extraction suggested the presence of methanol soluble low molecular weight molecules containing LA, while 1 % LA could be detected in the purified polymer fraction. These results suggested that the cells are producing a blend of polymers. A proteomic analysis of C. necator resting cells under P(3HB)/PLA production conditions provides new insights into the latent pathways involved in this process. This study is a proof of concept demonstrating that LA can polymerize in a non-modified organism and paves the way for new metabolic engineering approaches for lactic acid polymer production in the model bacterium C. necator H16.
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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
| | - Virginia Rivero-Buceta
- 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
| | - Isabel Pardo
- 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
| | - 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.
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2
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Sander K, Abel AJ, Friedline S, Sharpless W, Skerker J, Deutschbauer A, Clark DS, Arkin AP. Eliminating genes for a two-component system increases PHB productivity in Cupriavidus basilensis 4G11 under PHB suppressing, nonstress conditions. Biotechnol Bioeng 2024; 121:139-156. [PMID: 37638652 DOI: 10.1002/bit.28532] [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: 05/22/2023] [Revised: 08/07/2023] [Accepted: 08/10/2023] [Indexed: 08/29/2023]
Abstract
Species of bacteria from the genus Cupriavidus are known, in part, for their ability to produce high amounts of poly-hydroxybutyrate (PHB) making them attractive candidates for bioplastic production. The native synthesis of PHB occurs during periods of metabolic stress, and the process regulating the initiation of PHB accumulation in these organisms is not fully understood. Screening an RB-TnSeq transposon library of Cupriavidus basilensis 4G11 allowed us to identify two genes of an apparent, uncharacterized two-component system, which when omitted from the genome enable increased PHB productivity in balanced, nonstress growth conditions. We observe average increases in PHB productivity of 56% and 41% relative to the wildtype parent strain upon deleting each gene individually from the genome. The increased PHB phenotype disappears, however, in nitrogen-free unbalanced growth conditions suggesting the phenotype is specific to fast-growing, replete, nonstress growth. Bioproduction modeling suggests this phenotype could be due to a decreased reliance on metabolic stress induced by nitrogen limitation to initiate PHB production in the mutant strains. Due to uncertainty in the two-component system's input signal and regulon, the mechanism by which these genes impart this phenotype remains unclear. Such strains may allow for the use of single-stage, continuous bioreactor systems, which are far simpler than many PHB bioproduction schemes used previously, given a similar product yield to batch systems in such a configuration. Bioproductivity modeling suggests that omitting this regulation in the cells may increase PHB productivity up to 24% relative to the wildtype organism when using single-stage continuous systems. This work expands our understanding of the regulation of PHB accumulation in Cupriavidus, in particular the initiation of this process upon transition into unbalanced growth regimes.
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Affiliation(s)
- Kyle Sander
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
- Department of Bioengineering, University of California, Berkeley, California, USA
| | - Anthony J Abel
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California, USA
| | - Skyler Friedline
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
- Department of Bioengineering, University of California, Berkeley, California, USA
| | - William Sharpless
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
| | - Jeffrey Skerker
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
- Department of Bioengineering, University of California, Berkeley, California, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Adam Deutschbauer
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Douglas S Clark
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California, USA
| | - Adam P Arkin
- Center for the Utilization of Biological Engineering in Space, Berkeley, California, USA
- Department of Bioengineering, University of California, Berkeley, California, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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3
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Mitra R, Xu T, Chen GQ, Xiang H, Han J. An updated overview on the regulatory circuits of polyhydroxyalkanoates synthesis. Microb Biotechnol 2021; 15:1446-1470. [PMID: 34473895 PMCID: PMC9049629 DOI: 10.1111/1751-7915.13915] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 08/20/2021] [Accepted: 08/23/2021] [Indexed: 11/30/2022] Open
Abstract
Polyhydroxyalkanoates (PHA) are a promising and sustainable alternative to the petroleum‐based synthetic plastics. Regulation of PHA synthesis is receiving considerable importance as engineering the regulatory factors might help developing strains with improved PHA‐producing abilities. PHA synthesis is dedicatedly regulated by a number of regulatory networks. They tightly control the PHA content, granule size and their distribution in cells. Most PHA‐accumulating microorganisms have multiple regulatory networks that impart a combined effect on PHA metabolism. Among them, several factors ranging from global to specific regulators, have been identified and characterized till now. This review is an attempt to categorically summarize the diverse regulatory circuits that operate in some important PHA‐producing microorganisms. However, in several organisms, the detailed mechanisms involved in the regulation of PHA synthesis is not well‐explored and hence further research is needed. The information presented in this review might help researcher to identify the prevailing research gaps in PHA regulation.
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Affiliation(s)
- Ruchira Mitra
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,International College, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tong Xu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Guo-Qiang Chen
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Hua Xiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jing Han
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, 100049, China
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4
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Müller-Santos M, Koskimäki JJ, Alves LPS, de Souza EM, Jendrossek D, Pirttilä AM. The protective role of PHB and its degradation products against stress situations in bacteria. FEMS Microbiol Rev 2021; 45:fuaa058. [PMID: 33118006 DOI: 10.1093/femsre/fuaa058] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 10/26/2020] [Indexed: 12/15/2022] Open
Abstract
Many bacteria produce storage biopolymers that are mobilized under conditions of metabolic adaptation, for example, low nutrient availability and cellular stress. Polyhydroxyalkanoates are often found as carbon storage in Bacteria or Archaea, and of these polyhydroxybutyrate (PHB) is the most frequently occurring PHA type. Bacteria usually produce PHB upon availability of a carbon source and limitation of another essential nutrient. Therefore, it is widely believed that the function of PHB is to serve as a mobilizable carbon repository when bacteria face carbon limitation, supporting their survival. However, recent findings indicate that bacteria switch from PHB synthesis to mobilization under stress conditions such as thermal and oxidative shock. The mobilization products, 3-hydroxybutyrate and its oligomers, show a protective effect against protein aggregation and cellular damage caused by reactive oxygen species and heat shock. Thus, bacteria should have an environmental monitoring mechanism directly connected to the regulation of the PHB metabolism. Here, we review the current knowledge on PHB physiology together with a summary of recent findings on novel functions of PHB in stress resistance. Potential applications of these new functions are also presented.
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Affiliation(s)
- Marcelo Müller-Santos
- Department of Biochemistry and Molecular Biology, Federal University of Paraná - UFPR, Setor de Ciências Biológicas, Centro Politécnico, Jardim da Américas, CEP: 81531-990, Caixa Postal: 190-46, Curitiba, Paraná, Brazil
| | - Janne J Koskimäki
- Ecology and Genetics Research Unit, University of Oulu, Pentti Kaiteran katu 1, P.O. Box 3000, FI-90014 Oulu, Finland
| | - Luis Paulo Silveira Alves
- Department of Biochemistry and Molecular Biology, Federal University of Paraná - UFPR, Setor de Ciências Biológicas, Centro Politécnico, Jardim da Américas, CEP: 81531-990, Caixa Postal: 190-46, Curitiba, Paraná, Brazil
| | - Emanuel Maltempi de Souza
- Department of Biochemistry and Molecular Biology, Federal University of Paraná - UFPR, Setor de Ciências Biológicas, Centro Politécnico, Jardim da Américas, CEP: 81531-990, Caixa Postal: 190-46, Curitiba, Paraná, Brazil
| | - Dieter Jendrossek
- Institute of Microbiology, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
| | - Anna Maria Pirttilä
- Ecology and Genetics Research Unit, University of Oulu, Pentti Kaiteran katu 1, P.O. Box 3000, FI-90014 Oulu, Finland
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Sindhu R, Madhavan A, Arun KB, Pugazhendhi A, Reshmy R, Awasthi MK, Sirohi R, Tarafdar A, Pandey A, Binod P. Metabolic circuits and gene regulators in polyhydroxyalkanoate producing organisms: Intervention strategies for enhanced production. BIORESOURCE TECHNOLOGY 2021; 327:124791. [PMID: 33579565 DOI: 10.1016/j.biortech.2021.124791] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/19/2021] [Accepted: 01/23/2021] [Indexed: 06/12/2023]
Abstract
Worldwide worries upsurge concerning environmental pollutions triggered by the accumulation of plastic wastes. Biopolymers are promising candidates for resolving these difficulties by replacing non-biodegradable plastics. Among biopolymers, polyhydroxyalkanoates (PHAs), are natural polymers that are synthesized and accumulated in a range of microorganisms, are considered as promising biopolymers since they have biocompatibility, biodegradability, and other physico-chemical properties comparable to those of synthetic plastics. Consequently, considerable research have been attempted to advance a better understanding of mechanisms related to the metabolic synthesis and characteristics of PHAs and to develop native and recombinant microorganisms that can proficiently produce PHAs comprising desired monomers with high titer and productivity for industrial applications. Recent developments in metabolic engineering and synthetic biology applied to enhance PHA synthesis include, promoter engineering, ribosome-binding site (RBS) engineering, development of synthetic constructs etc. This review gives a brief overview of metabolic routes and regulators of PHA production and its intervention strategies.
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Affiliation(s)
- Raveendran Sindhu
- Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695 019, Kerala, India
| | - Aravind Madhavan
- Rajiv Gandhi Centre for Biotechnology, Trivandrum 695 014, Kerala, India
| | - K B Arun
- Rajiv Gandhi Centre for Biotechnology, Trivandrum 695 014, Kerala, India
| | - Arivalagan Pugazhendhi
- Innovative Green Product Synthesis and Renewable Environment Development Research Group, Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
| | - R Reshmy
- Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara 690 110, Kerala, India
| | - Mukesh Kumar Awasthi
- College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi Province 712100, PR China
| | - Ranjna Sirohi
- Department of Post Harvest Process and Food Engineering, G.B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand 263 145, India
| | - Ayon Tarafdar
- Divison of Livestock Production and Management, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly 243 122, Uttar Pradesh, India
| | - Ashok Pandey
- Centre for Innovation and Translational Research, CSIR- Indian Institute for Toxicology Research (CSIR-IITR), 31 MG Marg, Lucknow 226 001, India
| | - Parameswaran Binod
- Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695 019, Kerala, India.
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6
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Wang P, Yin Y, Wang X, Wen J. Enhanced ascomycin production in Streptomyces hygroscopicus var. ascomyceticus by employing polyhydroxybutyrate as an intracellular carbon reservoir and optimizing carbon addition. Microb Cell Fact 2021; 20:70. [PMID: 33731113 PMCID: PMC7968196 DOI: 10.1186/s12934-021-01561-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 03/08/2021] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Ascomycin is a multifunctional antibiotic produced by Streptomyces hygroscopicus var. ascomyceticus. As a secondary metabolite, the production of ascomycin is often limited by the shortage of precursors during the late fermentation phase. Polyhydroxybutyrate is an intracellular polymer accumulated by prokaryotic microorganisms. Developing polyhydroxybutyrate as an intracellular carbon reservoir for precursor synthesis is of great significance to improve the yield of ascomycin. RESULTS The fermentation characteristics of the parent strain S. hygroscopicus var. ascomyceticus FS35 showed that the accumulation and decomposition of polyhydroxybutyrate was respectively correlated with cell growth and ascomycin production. The co-overexpression of the exogenous polyhydroxybutyrate synthesis gene phaC and native polyhydroxybutyrate decomposition gene fkbU increased both the biomass and ascomycin yield. Comparative transcriptional analysis showed that the storage of polyhydroxybutyrate during the exponential phase accelerated biosynthesis processes by stimulating the utilization of carbon sources, while the decomposition of polyhydroxybutyrate during the stationary phase increased the biosynthesis of ascomycin precursors by enhancing the metabolic flux through primary pathways. The comparative analysis of cofactor concentrations confirmed that the biosynthesis of polyhydroxybutyrate depended on the supply of NADH. At low sugar concentrations found in the late exponential phase, the optimization of carbon source addition further strengthened the polyhydroxybutyrate metabolism by increasing the total concentration of cofactors. Finally, in the fermentation medium with 22 g/L starch and 52 g/L dextrin, the ascomycin yield of the co-overexpression strain was increased to 626.30 mg/L, which was 2.11-fold higher than that of the parent strain in the initial medium (296.29 mg/L). CONCLUSIONS Here we report for the first time that polyhydroxybutyrate metabolism is beneficial for cell growth and ascomycin production by acting as an intracellular carbon reservoir, stored as polymers when carbon sources are abundant and depolymerized into monomers for the biosynthesis of precursors when carbon sources are insufficient. The successful application of polyhydroxybutyrate in increasing the output of ascomycin provides a new strategy for improving the yields of other secondary metabolites.
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Affiliation(s)
- Pan Wang
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Ying Yin
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Xin Wang
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Jianping Wen
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China. .,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.
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7
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Arai S, Sakakibara S, Mareschal R, Ooi T, Zinn M, Matsumoto K. Biosynthesis of Random-Homo Block Copolymer Poly[Glycolate- ran-3-Hydroxybutyrate (3HB)]- b-Poly(3HB) Using Sequence-Regulating Chimeric Polyhydroxyalkanoate Synthase in Escherichia coli. Front Bioeng Biotechnol 2020; 8:612991. [PMID: 33364233 PMCID: PMC7752996 DOI: 10.3389/fbioe.2020.612991] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 11/16/2020] [Indexed: 11/13/2022] Open
Abstract
Glycolate (GL)-containing polyhydroxyalkanoate (PHA) was synthesized in Escherichia coli expressing the engineered chimeric PHA synthase PhaC AR and coenzyme A transferase. The cells produced poly[GL-co-3-hydroxybutyrate (3HB)] with the supplementation of GL and 3HB, thus demonstrating that PhaC AR is the first known class I PHA synthase that is capable of incorporating GL units. The triad sequence analysis using 1H nuclear magnetic resonance indicated that the obtained polymer was composed of two distinct regions, a P(GL-ran-3HB) random segment and P(3HB) homopolymer segment. The random segment was estimated to contain a 71 mol% GL molar ratio, which was much greater than the value (15 mol%) previously achieved by using PhaC1 P s STQK. Differential scanning calorimetry analysis of the polymer films supported the presence of random copolymer and homopolymer phases. The solvent fractionation of the polymer indicated the presence of a covalent linkage between these segments. Therefore, it was concluded that PhaC AR synthesized a novel random-homo block copolymer, P(GL-ran-3HB)-b-P(3HB).
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Affiliation(s)
- Shuzo Arai
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Japan
| | - Sayaka Sakakibara
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Japan
| | - Robin Mareschal
- Department of Engineering, Hokkaido University, Sapporo, Japan
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis), Sion, Switzerland
| | - Toshihiko Ooi
- Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Sapporo, Japan
| | - Manfred Zinn
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis), Sion, Switzerland
| | - Ken’ichiro Matsumoto
- Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Sapporo, Japan
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Velázquez-Sánchez C, Espín G, Peña C, Segura D. The Modification of Regulatory Circuits Involved in the Control of Polyhydroxyalkanoates Metabolism to Improve Their Production. Front Bioeng Biotechnol 2020; 8:386. [PMID: 32426348 PMCID: PMC7204398 DOI: 10.3389/fbioe.2020.00386] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 04/07/2020] [Indexed: 11/13/2022] Open
Abstract
Poly-(3-hydroxyalkanoates) (PHAs) are bacterial carbon and energy storage compounds. These polymers are synthesized under conditions of nutritional imbalance, where a nutrient is growth-limiting while there is still enough carbon source in the medium. On the other side, the accumulated polymer is mobilized under conditions of nutrient accessibility or by limitation of the carbon source. Thus, it is well known that the accumulation of PHAs is affected by the availability of nutritional resources and this knowledge has been used to establish culture conditions favoring high productivities. In addition to this effect of the metabolic status on PHAs accumulation, several genetic regulatory networks have been shown to drive PHAs metabolism, so the expression of the PHAs genes is under the influence of global or specific regulators. These regulators are thought to coordinate PHAs synthesis and mobilization with the rest of bacterial physiology. While the metabolic and biochemical knowledge related to the biosynthesis of these polymers has led to the development of processes in bioreactors for high-level production and also to the establishment of strategies for metabolic engineering for the synthesis of modified biopolymers, the use of knowledge related to the regulatory circuits controlling PHAs metabolism for strain improvement is scarce. A better understanding of the genetic control systems involved could serve as the foundation for new strategies for strain modification in order to increase PHAs production or to adjust the chemical structure of these biopolymers. In this review, the regulatory systems involved in the control of PHAs metabolism are examined, with emphasis on those acting at the level of expression of the enzymes involved and their potential modification for strain improvement, both for higher titers, or manipulation of polymer properties. The case of the PHAs producer Azotobacter vinelandii is taken as an example of the complexity and variety of systems controlling the accumulation of these interesting polymers in response to diverse situations, many of which could be engineered to improve PHAs production.
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Affiliation(s)
- Claudia Velázquez-Sánchez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Carlos Peña
- Departamento Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Daniel Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
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9
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Yañez L, Conejeros R, Vergara-Fernández A, Scott F. Beyond Intracellular Accumulation of Polyhydroxyalkanoates: Chiral Hydroxyalkanoic Acids and Polymer Secretion. Front Bioeng Biotechnol 2020; 8:248. [PMID: 32318553 PMCID: PMC7147478 DOI: 10.3389/fbioe.2020.00248] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 03/10/2020] [Indexed: 01/05/2023] Open
Abstract
Polyhydroxyalkanoates (PHAs) are ubiquitous prokaryotic storage compounds of carbon and energy, acting as sinks for reducing power during periods of surplus of carbon source relative to other nutrients. With close to 150 different hydroxyalkanoate monomers identified, the structure and properties of these polyesters can be adjusted to serve applications ranging from food packaging to biomedical uses. Despite its versatility and the intensive research in the area over the last three decades, the market share of PHAs is still low. While considerable rich literature has accumulated concerning biochemical, physiological, and genetic aspects of PHAs intracellular accumulation, the costs of substrates and processing costs, including the extraction of the polymer accumulated in intracellular granules, still hampers a more widespread use of this family of polymers. This review presents a comprehensive survey and critical analysis of the process engineering and metabolic engineering strategies reported in literature aimed at the production of chiral (R)-hydroxycarboxylic acids (RHAs), either from the accumulated polymer or by bypassing the accumulation of PHAs using metabolically engineered bacteria, and the strategies developed to recover the accumulated polymer without using conventional downstream separations processes. Each of these topics, that have received less attention compared to PHAs accumulation, could potentially improve the economy of PHAs production and use. (R)-hydroxycarboxylic acids can be used as chiral precursors, thanks to its easily modifiable functional groups, and can be either produced de-novo or be obtained from recycled PHA products. On the other hand, efficient mechanisms of PHAs release from bacterial cells, including controlled cell lysis and PHA excretion, could reduce downstream costs and simplify the polymer recovery process.
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Affiliation(s)
- Luz Yañez
- Green Technology Research Group, Facultad de Ingeniería y Ciencias Aplicadas, Universidad de los Andes, Santiago, Chile
| | - Raúl Conejeros
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Alberto Vergara-Fernández
- Green Technology Research Group, Facultad de Ingeniería y Ciencias Aplicadas, Universidad de los Andes, Santiago, Chile
| | - Felipe Scott
- Green Technology Research Group, Facultad de Ingeniería y Ciencias Aplicadas, Universidad de los Andes, Santiago, Chile
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10
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Martínez-Martínez MDLA, González-Pedrajo B, Dreyfus G, Soto-Urzúa L, Martínez-Morales LJ. Phasin PhaP1 is involved in polyhydroxybutyrate granules morphology and in controlling early biopolymer accumulation in Azospirillum brasilense Sp7. AMB Express 2019; 9:155. [PMID: 31555910 PMCID: PMC6761214 DOI: 10.1186/s13568-019-0876-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/09/2019] [Indexed: 11/10/2022] Open
Abstract
Phasins are amphiphilic proteins involved in the regulation of the number and size of polyhydroxybutyrate (PHB) granules. The plant growth promoting bacterium Azospirillum brasilense Sp7 accumulates high quantities of bioplastic PHB as carbon and energy source. By analyzing the genome, we identified six genes that code for proteins with a Phasin_2 domain. To understand the role of A. brasilense Sp7 PhaP1 (PhaP1Abs) on PHB synthesis, the phaP1 gene (AMK58_RS17065) was deleted. The morphology of the PHB granules was analyzed by transmission electron microscopy (TEM) and the PHB produced was quantified under three different C:N ratios in cultures subjected to null or low-oxygen transfer. The results showed that PhaP1Abs is involved in PHB granules morphology and in controlling early biopolymer accumulation. Using RT-PCR it was found that phasin genes, except phaP4, are transcribed in accordance with the C:N ratio used for the growth of A. brasilense. phaP1, phaP2 and phaP3 genes were able to respond to the growth conditions tested. This study reports the first analysis of a phasin protein in A. brasilense Sp7.
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