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Urtuvia V, Ponce B, Andler R, Peña C, Diaz-Barrera A. Extended batch cultures for poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) production by Azotobacter vinelandii OP growing at different aeration rates. 3 Biotech 2022; 12:304. [PMID: 36276477 PMCID: PMC9525563 DOI: 10.1007/s13205-022-03380-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 09/23/2022] [Indexed: 11/29/2022] Open
Abstract
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a polymer produced by Azotobacter vinelandii OP. In the bioreactor, PHBV production and its molar composition are affected by aeration rate. PHBV production by A. vinelandii OP was evaluated using extended batch cultures at different aeration rates, which determined different oxygen transfer rates (OTR) in the cultures. Under the conditions evaluated, PHBV with different 3-hydroxyvalerate (3HV) fractions were obtained. In the cultures with a low OTR (6.7 mmol L-1 h-1, at 0.3 vvm), a PHBV content of 38% w w-1 with 9.1 mol % 3HV was achieved. The maximum PHBV production (72% w w-1) was obtained at a high OTR (18.2 mmol L-1 h-1, at 1.0 vvm), both at 48 h. Thus, PHBV production increased in the bioreactor with an increased aeration rate, but not the 3HV fraction in the polymer chain. An OTR of 24.9 mmol L-1 h-1 (at 2.1 vvm) was the most suitable for improving the PHBV content (61% w w-1) and a high 3HV fraction of 20.8 mol % (at 48 h); and volumetric productivity (0.15 g L-1 h-1). The findings indicate that the extended batch culture at 2.1 vvm is the most adequate mode of cultivation to produce higher biomass and PHBV with a high 3HV fraction. Overall, the results have shown that the PHBV production and 3HV fraction could be affected by the aeration rate and the proposed approach could be applied to implement cultivation strategies to optimize PHBV production for different biotechnological applications.
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Affiliation(s)
- Viviana Urtuvia
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147 Casilla 4059, Valparaíso, Chile
| | - Belén Ponce
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147 Casilla 4059, Valparaíso, Chile
| | - Rodrigo Andler
- Escuela de Ingeniería en Biotecnología, Centro de Biotecnología de los Recursos Naturales (Cenbio),Universidad Católica del Maule, Talca, Chile
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Alvaro Diaz-Barrera
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147 Casilla 4059, Valparaíso, Chile
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2
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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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3
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Díaz-Barrera A, Sanchez-Rosales F, Padilla-Córdova C, Andler R, Peña C. Molecular weight and guluronic/mannuronic ratio of alginate produced by Azotobacter vinelandii at two bioreactor scales under diazotrophic conditions. Bioprocess Biosyst Eng 2021; 44:1275-1287. [PMID: 33635396 DOI: 10.1007/s00449-021-02532-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/07/2021] [Indexed: 11/24/2022]
Abstract
Alginates can be used to elaborate hydrogels, and their properties depend on the molecular weight (MW) and the guluronic (G) and mannuronic (M) composition. In this study, the MW and G/M ratio were evaluated in cultures of Azotobacter vinelandii to 3 and 30 L scales at different oxygen transfer rates (OTRs) under diazotrophic conditions. An increase in the maximum OTR (OTRmax) improved the alginate production, reaching 3.3 ± 0.2 g L-1. In the cultures conducted to an OTR of 10.4 mmol L-1 h-1 (500 rpm), the G/M increased during the cell growth phase and decreased during the stationary phase; whereas, in the cultures at 19.2 mmol L-1 h-1 was constant throughout the cultivation. A higher alginate MW (520 ± 43 kDa) and G/M ratio (0.86 ± 0.01) were obtained in the cultures conducted at 10.4 mmol L-1 h-1. The OTR as a criterion to scale up alginate production allowed to replicate the concentration and the alginate production rate; however, it was not possible reproduce the MW and G/M ratio. Under a similar specific oxygen uptake rate (qO2) (approximately 65 mmol g-1 h-1) the alginate MW was similar (approximately 365 kDa) in both scales. The evidences revealed that the qO2 can be a parameter adequate to produce alginate MW similar in two bioreactor scales. Overall, the results have shown that the alginate composition could be affected by cellular respiration, and from a technological perspective the evidences contribute to the design process based on oxygen consumption to produce alginates defined.
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Affiliation(s)
- Alvaro Díaz-Barrera
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147, 4059, Casilla, Valparaíso, Chile.
| | - Francisco Sanchez-Rosales
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147, 4059, Casilla, Valparaíso, Chile.,Facultad de Ciencias Tecnológicas, Universidad Nacional de Agricultura, Carretera a Dulce Nombre de Culmí, km 212, Barrio El Espino, Catacamas, Honduras
| | - Claudio Padilla-Córdova
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147, 4059, Casilla, Valparaíso, Chile
| | - Rodrigo Andler
- Escuela de Ingeniería en Biotecnología, Universidad Católica del Maule, Talca, Chile
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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4
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Gómez-Hernández E, Salgado-Lugo H, Segura D, García A, Díaz-Barrera A, Peña C. Production of Poly-3-Hydroxybutyrate (P3HB) with Ultra-High Molecular Weight (UHMW) by Mutant Strains of Azotobacter vinelandii Under Microaerophilic Conditions. Appl Biochem Biotechnol 2020; 193:79-95. [PMID: 32813183 DOI: 10.1007/s12010-020-03384-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 06/22/2020] [Indexed: 11/28/2022]
Abstract
Poly-3-hydroxybutyrate (P3HB) is a biopolymer, which presents characteristics similar to those of plastics derived from the petrochemical industry. The thermomechanical properties and biodegradability of P3HB are influenced by its molecular weight (MW). The aim of the present study was to evaluate the changes of the molecular weight of P3HB as a function of oxygen transfer rate (OTR) in the cultures using two strains of Azotobacter vinelandii, a wild-type strain OP, and PhbZ1 mutant with a P3HB depolymerase inactivated. Both strains were grown in a bioreactor under different OTR conditions. An inverse relationship was found between the average molecular weight of P3HB and the OTRmax, obtaining a polymer with a maximal MW (8000-10,000 kDa) from the cultures developed at OTRmax of 5 mmol L-1 h-1 using both strains, with respect to the cultures conducted at 8 and 11 mmol L-1 h-1, which produced a P3HB between 4000 and 5000 kDa. The increase in MW of P3HB was related to the activity of enzymes involved in the synthesis and depolymerization. Overall, our results show that it is possible to modulate the average molecular weight of P3HB by manipulating oxygen transfer conditions with both strains (OP and PhbZ1 mutant) of A. vinelandii.
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Affiliation(s)
- Elsa Gómez-Hernández
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Mor, Mexico
| | - Holjes Salgado-Lugo
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Mor, Mexico
| | - Daniel Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Mor, Mexico
| | - Andrés García
- Laboratorio de Biotecnología Ambiental, Centro de Investigación en Biotecnología, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico
| | - Alvaro Díaz-Barrera
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147 Casilla, 4059, Valparaíso, Chile
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Mor, Mexico.
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5
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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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6
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Batista MB, Teixeira CS, Sfeir MZT, Alves LPS, Valdameri G, Pedrosa FDO, Sassaki GL, Steffens MBR, de Souza EM, Dixon R, Müller-Santos M. PHB Biosynthesis Counteracts Redox Stress in Herbaspirillum seropedicae. Front Microbiol 2018; 9:472. [PMID: 29599762 PMCID: PMC5862806 DOI: 10.3389/fmicb.2018.00472] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 02/28/2018] [Indexed: 11/25/2022] Open
Abstract
The ability of bacteria to produce polyhydroxyalkanoates such as poly(3-hydroxybutyrate) (PHB) enables provision of a carbon storage molecule that can be mobilized under demanding physiological conditions. However, the precise function of PHB in cellular metabolism has not been clearly defined. In order to determine the impact of PHB production on global physiology, we have characterized the properties of a ΔphaC1 mutant strain of the diazotrophic bacterium Herbaspirillum seropedicae. The absence of PHB in the mutant strain not only perturbs redox balance and increases oxidative stress, but also influences the activity of the redox-sensing Fnr transcription regulators, resulting in significant changes in expression of the cytochrome c-branch of the electron transport chain. The synthesis of PHB is itself dependent on the Fnr1 and Fnr3 proteins resulting in a cyclic dependency that couples synthesis of PHB with redox regulation. Transcriptional profiling of the ΔphaC1 mutant reveals that the loss of PHB synthesis affects the expression of many genes, including approximately 30% of the Fnr regulon.
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Affiliation(s)
- Marcelo B Batista
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil.,Department of Molecular Microbiology, John Innes Centre, Norwich, United Kingdom
| | - Cícero S Teixeira
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
| | - Michelle Z T Sfeir
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
| | - Luis P S Alves
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
| | - Glaucio Valdameri
- Department of Clinical Analysis, Universidade Federal do Paraná, Curitiba, Brazil
| | | | - Guilherme L Sassaki
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
| | - Maria B R Steffens
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
| | - Emanuel M de Souza
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, Norwich, United Kingdom
| | - Marcelo Müller-Santos
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Brazil
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7
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Yoneyama F, Yamamoto M, Hashimoto W, Murata K. Production of polyhydroxybutyrate and alginate from glycerol by Azotobacter vinelandii under nitrogen-free conditions. Bioengineered 2015; 6:209-17. [PMID: 25880041 DOI: 10.1080/21655979.2015.1040209] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Glycerol is an interesting feedstock for biomaterials such as biofuels and bioplastics because of its abundance as a by-product during biodiesel production. Here we demonstrate glycerol metabolism in the nitrogen-fixing species Azotobacter vinelandii through metabolomics and nitrogen-free bacterial production of biopolymers, such as poly-d-3-hydroxybutyrate (PHB) and alginate, from glycerol. Glycerol-3-phosphate was accumulated in A. vinelandii cells grown on glycerol to the exponential phase, and its level drastically decreased in the cells grown to the stationary growth phase. A. vinelandii also overexpressed the glycerol-3-phosphate dehydrogenase gene when it was grown on glycerol. These results indicate that glycerol was first converted to glycerol-3-phosphate by glycerol kinase. Other molecules with industrial interests, such as lactic acid and amino acids including γ-aminobutyric acid, have also been accumulated in the bacterial cells grown on glycerol. Transmission electron microscopy revealed that glycerol-grown A. vinelandii stored PHB within the cells. The PHB production level reached 33% per dry cell weight in nitrogen-free glycerol medium. When grown on glycerol, alginate-overproducing mutants generated through chemical mutagenesis produced 2-fold the amount of alginate from glycerol than the parental wild-type strain. To the best of our knowledge, this is the first report on bacterial production of biopolymers from glycerol without addition of any nitrogen source.
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Affiliation(s)
- Fuminori Yoneyama
- a Division of Food Science and Biotechnology ; Graduate School of Agriclture Kyoto University ; Uji , Kyoto , Japan
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8
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Genome sequence of Azotobacter vinelandii, an obligate aerobe specialized to support diverse anaerobic metabolic processes. J Bacteriol 2009; 191:4534-45. [PMID: 19429624 DOI: 10.1128/jb.00504-09] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Azotobacter vinelandii is a soil bacterium related to the Pseudomonas genus that fixes nitrogen under aerobic conditions while simultaneously protecting nitrogenase from oxygen damage. In response to carbon availability, this organism undergoes a simple differentiation process to form cysts that are resistant to drought and other physical and chemical agents. Here we report the complete genome sequence of A. vinelandii DJ, which has a single circular genome of 5,365,318 bp. In order to reconcile an obligate aerobic lifestyle with exquisitely oxygen-sensitive processes, A. vinelandii is specialized in terms of its complement of respiratory proteins. It is able to produce alginate, a polymer that further protects the organism from excess exogenous oxygen, and it has multiple duplications of alginate modification genes, which may alter alginate composition in response to oxygen availability. The genome analysis identified the chromosomal locations of the genes coding for the three known oxygen-sensitive nitrogenases, as well as genes coding for other oxygen-sensitive enzymes, such as carbon monoxide dehydrogenase and formate dehydrogenase. These findings offer new prospects for the wider application of A. vinelandii as a host for the production and characterization of oxygen-sensitive proteins.
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Galindo E, Peña C, Núñez C, Segura D, Espín G. Molecular and bioengineering strategies to improve alginate and polydydroxyalkanoate production by Azotobacter vinelandii. Microb Cell Fact 2007; 6:7. [PMID: 17306024 PMCID: PMC1805506 DOI: 10.1186/1475-2859-6-7] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Accepted: 02/16/2007] [Indexed: 12/01/2022] Open
Abstract
Several aspects of alginate and PHB synthesis in Azotobacter vinelandii at a molecular level have been elucidated in articles published during the last ten years. It is now clear that alginate and PHB synthesis are under a very complex genetic control. Genetic modification of A. vinelandii has produced a number of very interesting mutants which have particular traits for alginate production. One of these mutants has been shown to produce the alginate with the highest mean molecular mass so far reported. Recent work has also shed light on the factors determining molecular mass distribution; the most important of these being identified as; dissolved oxygen tension and specific growth rate. The use of specific mutants has been very useful for the correct analysis and interpretation of the factors affecting polymerization. Recent scale-up/down work on alginate production has shown that oxygen limitation is crucial for producing alginate of high molecular mass, a condition which is optimized in shake flasks and which can now be reproduced in stirred fermenters. It is clear that the phenotypes of mutants grown on plates are not necessarily reproducible when the strains are tested in lab or bench scale fermenters. In the case of PHB, A. vinelandii has shown itself able to produce relatively large amounts of this polymer of high molecular weight on cheap substrates, even allowing for simple extraction processes. The development of fermentation strategies has also shown promising results in terms of improving productivity. The understanding of the regulatory mechanisms involved in the control of PHB synthesis, and of its metabolic relationships, has increased considerably, making way for new potential strategies for the further improvement of PHB production. Overall, the use of a multidisciplinary approach, integrating molecular and bioengineering aspects is a necessity for optimizing alginate and PHB production in A. vinelandii.
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Affiliation(s)
- Enrique Galindo
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional, Autónoma de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional, Autónoma de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Daniel Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
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Stubbe J, Tian J, He A, Sinskey AJ, Lawrence AG, Liu P. NONTEMPLATE-DEPENDENT POLYMERIZATION PROCESSES: Polyhydroxyalkanoate Synthases as a Paradigm. Annu Rev Biochem 2005; 74:433-80. [PMID: 15952894 DOI: 10.1146/annurev.biochem.74.082803.133013] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review focuses on nontemplate-dependent polymerases that use water-soluble substrates and convert them into water-insoluble polymers that form granules or inclusions within the cell. The initial part of the review summarizes briefly the current knowledge of polymer formation catalyzed by starch and glycogen synthases, polyphosphate kinase (a polymerase), cyanophycin synthetases, and rubber synthases. Specifically, our current understanding of their mechanisms of initiation, elongation (including granule formation), termination, remodeling, and polymer reutilization will be presented. General underlying principles that govern these types of polymerization reactions will be enumerated as a paradigm for all nontemplate-dependent polymerizations. The bulk of the review then focuses on polyhydroxyalkanoate (PHA) synthases that generate polyoxoesters. These enzymes are of interest as they generate biodegradable polymers. Our current knowledge of PHA production and utilization in vitro and in vivo as well as the contribution of many proteins to these processes will be reviewed.
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Affiliation(s)
- Joanne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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11
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Korotkova N, Chistoserdova L, Lidstrom ME. Poly-beta-hydroxybutyrate biosynthesis in the facultative methylotroph methylobacterium extorquens AM1: identification and mutation of gap11, gap20, and phaR. J Bacteriol 2002; 184:6174-81. [PMID: 12399487 PMCID: PMC151960 DOI: 10.1128/jb.184.22.6174-6181.2002] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2002] [Accepted: 08/20/2002] [Indexed: 11/20/2022] Open
Abstract
Methylobacterium extorquens AM1, a serine cycle facultative methylotroph, accumulates poly-beta-hydroxybutyrate (PHB) as a carbon and energy reserve material during growth on both multicarbon- and single-carbon substrates. Recently, the identification and mutation of the genes involved in the biosynthesis and degradation of PHB have been described for this bacterium, demonstrating that two of the genes of the PHB cycle (phaA and phaB) are also involved in C(1) and C(2) metabolism, as part of a novel pathway for glyoxylate regeneration in the serine cycle (N. Korotkova and M. E. Lidstrom, J. Bacteriol. 183:1038-1046, 2001; N. Korotkova, L. Chistoserdova, V. Kuksa, and M. E. Lidstrom, J. Bacteriol. 184:1750-1758, 2002). In this work, three new genes involved in PHB biosynthesis in this bacterium have been investigated via mutation and phenotypic analysis: gap11, gap20, and phaR. We demonstrate that gap11 and gap20 encode two major granule-associated proteins (phasins) and that mutants with mutations in these genes are defective in PHB production and also in growth on C(2) compounds, while they show wild-type growth characteristics on C(1) or multicarbon compounds. The phaR mutant shows defects in both PHB accumulation and growth characteristics when grown on C(1) compounds and has defects in PHB accumulation but grows normally on C(3) and C(4) compounds, while both PHB accumulation and growth rate are at wild-type levels during growth on C(2) compounds. Our results suggest that this phenotype is due to altered fluxes of acetyl coenzyme A (CoA), a major intermediate in C(1), C(2), and heterotrophic metabolism in M. extorquens AM1, as well as the entry metabolite for the PHB cycle. Therefore, it seems likely that PhaR acts to control acetyl-CoA flux to PHB in this methylotrophic bacterium.
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Affiliation(s)
- Natalia Korotkova
- Department of Chemical Engineering, University of Washington, Seattle 98195-1750, USA
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12
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Peralta-Gil M, Segura D, Guzmán J, Servín-González L, Espín G. Expression of the Azotobacter vinelandii poly-beta-hydroxybutyrate biosynthetic phbBAC operon is driven by two overlapping promoters and is dependent on the transcriptional activator PhbR. J Bacteriol 2002; 184:5672-7. [PMID: 12270825 PMCID: PMC139623 DOI: 10.1128/jb.184.20.5672-5677.2002] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Azotobacter vinelandii phbBAC genes encode the enzymes for poly-beta-hydroxybutyrate (PHB) synthesis. The phbR gene, which is located upstream of and in the opposite direction of phbBAC, encodes PhbR, a transcriptional activator which is a member of the AraC family of activators. Here we report that a mutation in phbR reduced PHB accumulation and transcription of a phbB-lacZ fusion. We also report that phbB is transcribed from two overlapping promoters, p(B)1 and p(B)2. The region corresponding to the -35 region of p(B)1 overlaps the p(B)2 -10 region. In the phbR mutant, expression of phbB from the p(B)1 promoter is significantly reduced, whereas expression from the p(B)2 promoter is slightly increased. Two phbR promoters, p(R)1 and p(R)2, were also identified. Transcription from p(R)2 was shown to be dependent on sigma(S). Six conserved 18-bp sites, designated R1 to R6, are present within the phbR-phbB intergenic region and are proposed to be putative binding targets for PhbR. R1 overlaps the -35 region of the p(B)1 promoter. A model for the regulation of phbB transcription by PhbR is proposed.
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Affiliation(s)
- Martín Peralta-Gil
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca Morelos 62250, Mexico
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