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Wei X, Chen Z, Liu A, Yang L, Xu Y, Cao M, He N. Advanced strategies for metabolic engineering of Bacillus to produce extracellular polymeric substances. Biotechnol Adv 2023; 67:108199. [PMID: 37330153 DOI: 10.1016/j.biotechadv.2023.108199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 05/24/2023] [Accepted: 06/11/2023] [Indexed: 06/19/2023]
Abstract
Extracellular polymeric substances are mainly synthesized via a variety of biosynthetic pathways in bacteria. Bacilli-sourced extracellular polymeric substances, such as exopolysaccharides (EPS) and poly-γ-glutamic acid (γ-PGA), can serve as active ingredients and hydrogels, and have other important industrial applications. However, the functional diversity and widespread applications of these extracellular polymeric substances, are hampered by their low yields and high costs. Biosynthesis of extracellular polymeric substances is very complex in Bacillus, and there is no detailed elucidation of the reactions and regulations among various metabolic pathways. Therefore, a better understanding of the metabolic mechanisms is required to broaden the functions and increase the yield of extracellular polymeric substances. This review systematically summarizes the biosynthesis and metabolic mechanisms of extracellular polymeric substances in Bacillus, providing an in-depth understanding of the relationships between EPS and γ-PGA synthesis. This review provides a better clarification of Bacillus metabolic mechanisms during extracellular polymeric substance secretion and thus benefits their application and commercialization.
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Affiliation(s)
- Xiaoyu Wei
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen 361005, China
| | - Zhen Chen
- College of Life Science, Xinyang Normal University, Xinyang 464000, China.
| | - Ailing Liu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen 361005, China
| | - Lijie Yang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen 361005, China
| | - Yiyuan Xu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen 361005, China
| | - Mingfeng Cao
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen 361005, China; Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361005, China.
| | - Ning He
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen 361005, China.
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Nair P, Navale GR, Dharne MS. Poly-gamma-glutamic acid biopolymer: a sleeping giant with diverse applications and unique opportunities for commercialization. BIOMASS CONVERSION AND BIOREFINERY 2023; 13:4555-4573. [PMID: 33824848 PMCID: PMC8016157 DOI: 10.1007/s13399-021-01467-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/19/2021] [Accepted: 03/23/2021] [Indexed: 05/06/2023]
Abstract
Poly-gamma-glutamic acid (γ-PGA) is a biodegradable, non-toxic, ecofriendly, and non-immunogenic biopolymer. Its phenomenal properties have gained immense attention in the field of regenerative medicine, the food industry, wastewater treatment, and even in 3D printing bio-ink. The γ-PGA has the potential to replace synthetic non-degradable counterparts, but the main obstacle is the high production cost and lower productivity. Extensive research has been carried out to reduce the production cost by using different waste; however, it is unable to match the commercialization needs. This review focuses on the biosynthetic mechanism of γ-PGA, its production using the synthetic medium as well as different wastes by L-glutamic acid-dependent and independent microbial strains. Furthermore, various metabolic engineering strategies and the recovery processes for γ-PGA and their possible applications are discussed. Finally, highlights on the challenges and unique approaches to reduce the production cost and to increase the productivity for commercialization of γ-PGA are also summarized.
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Affiliation(s)
- Pranav Nair
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- National Collection of Industrial Microorganisms (NCIM), CSIR-National Chemical Laboratory, Pune, 411008 India
| | - Govinda R. Navale
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- National Collection of Industrial Microorganisms (NCIM), CSIR-National Chemical Laboratory, Pune, 411008 India
| | - Mahesh S. Dharne
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- National Collection of Industrial Microorganisms (NCIM), CSIR-National Chemical Laboratory, Pune, 411008 India
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Xia X, Lan S, Li X, Xie Y, Liang Y, Yan P, Chen Z, Xing Y. Characterization and coagulation-flocculation performance of a composite flocculant in high-turbidity drinking water treatment. CHEMOSPHERE 2018; 206:701-708. [PMID: 29783055 DOI: 10.1016/j.chemosphere.2018.04.159] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 04/23/2018] [Accepted: 04/26/2018] [Indexed: 06/08/2023]
Abstract
Klebsiella variicola B16, a microbial bioflocculant (MBF-B16)-producing bacteria, was isolated and identified by its 16S rRNA sequence, biochemical properties, and physiological characteristics. The effects of culture conditions on MBF-B16 production, including carbon source, nitrogen source, C/N ratio, initial pH, and culture temperature, were investigated in this study. Results showed that 6.96 g of MBF-B16 could be extracted from a 1-L culture broth under optimized conditions. Chemical analysis showed that polysaccharide and protein were the main components. The neutral sugar consisted of galactose only, which was proposed in Klebsiella genus for the first time. In addition, a composite flocculant (CF) that contains polyaluminum ferric chloride (PAFC) and MBF-B16 for the removal of turbidity and SS in drinking water was optimized by response surface methodology. CF could reduce PAFC dosage by about 56.2-72%. Charge neutralization and adsorption bridging effect were the primary flocculation mechanisms.
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Affiliation(s)
- Xiang Xia
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; University of Chinese Academy of Sciences, 100049, Beijing, PR China
| | - Shuhuan Lan
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China
| | - Xudong Li
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; University of Chinese Academy of Sciences, 100049, Beijing, PR China
| | - Yifei Xie
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; University of Chinese Academy of Sciences, 100049, Beijing, PR China.
| | - Yajie Liang
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; University of Chinese Academy of Sciences, 100049, Beijing, PR China
| | - Peihan Yan
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, 610041, Chengdu, PR China; University of Chinese Academy of Sciences, 100049, Beijing, PR China
| | - Zhengyang Chen
- Key Laboratory of Synergetic Control and Joint Remediation for Soil & Water Pollution (SEKL-SW), Chengdu University of Technology State Environmental Protection, Chengdu University of Technology, 610059, Chengdu, PR China
| | - Yunxiao Xing
- College of Chemistry and Materials Science, Sichuan Normal University, 610066, Sichuan, PR China
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Solution scattering study of the Bacillus subtilis PgdS enzyme involved in poly-γ-glutamic acids degradation. PLoS One 2018; 13:e0195355. [PMID: 29608608 PMCID: PMC5880399 DOI: 10.1371/journal.pone.0195355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 03/21/2018] [Indexed: 11/19/2022] Open
Abstract
The PgdS enzyme is a poly-γ-glutamic (γ-PGA) hydrolase, which has potential application for a controllable degradation of γ-PGA by enzymatic depolymerization; however, the structure of PgdS is still unknown. Here, to study in detail the full-length PgdS structure, we analyze the low-resolution architecture of PgdS hydrolase from Bacillus subtilis in solution using small angle X-ray scattering (SAXS) method. Combining with other methods, like dynamic light scattering and mutagenesis analyses, a model for the full length structure and the possible substrate delivery route of PgdS are proposed. The results will provide useful hints for future investigations into the mechanisms of γ-PGA degradation by the PgdS hydrolase and may provide valuable practical information.
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Liu P, Chen Z, Yang L, Li Q, He N. Increasing the bioflocculant production and identifying the effect of overexpressing epsB on the synthesis of polysaccharide and γ-PGA in Bacillus licheniformis. Microb Cell Fact 2017; 16:163. [PMID: 28950882 PMCID: PMC5615475 DOI: 10.1186/s12934-017-0775-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 09/18/2017] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Polysaccharides and poly-γ-glutamic acid (γ-PGA) are biomacromolecules that have been reported as bioflocculants, and they exhibit high flocculating activity in many industrial applications. Bacillus licheniformis CGMCC 2876 can produce polysaccharide and γ-PGA bioflocculants under different culture conditions. Several key genes are involved in the metabolic pathway of polysaccharides in B. licheniformis, but the impacts of the regulation of these genes on the production of polysaccharide bioflocculants have not been illustrated completely. To increase the bioflocculant production and identify the correlation between the synthesis of polysaccharides and γ-PGA in B. licheniformis, a few key genes were investigated to explore their influence on the synthesis of the bioflocculants. RESULTS Overexpressing epsB from the eps gene cluster not only improved the bioflocculant crude yield by 13.98% but also enhanced the flocculating activity by 117.92%. The composition of the bioflocculant from the epsB recombinant strain was 28.95% total sugar, 3.464% protein and 44.03% γ-PGA, while in the original strain, these components represented 53.67%, 3.246% and 34.13%, respectively. In combination with an analysis of the transcriptional levels of several key genes involved in γ-PGA synthesis in B. licheniformis, we inferred that epsB played a key role in the synthesis of both polysaccharide and γ-PGA. The bioflocculant production of the epsB recombinant strain was further evaluated during batch fermentation in a 2 L fermenter; the flocculating activity reached 9612.75 U/mL, and the bioflocculant yield reached 10.26 g/L after 72 h, representing increases of 224% and 36.62%, respectively, compared with the original strain. Moreover, we found that the tandem expression of phosphoglucomutase (pgcA) and UTP-glucose-1-phosphate uridylyltransferase (gtaB1) could enhance the crude yield of the bioflocculant by 20.77% and that the overexpression of epsA could enhance the bioflocculant yield by 23.70% compared with the original strain. CONCLUSIONS This study provides a new method to greatly increase the bioflocculant production in B. licheniformis, and it demonstrates the correlation between the biosynthesis of polysaccharide and γ-PGA during EPS fermentation by regulating the expression of EpsB.
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Affiliation(s)
- Peize Liu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005 People’s Republic of China
- The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Zhen Chen
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005 People’s Republic of China
- The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Lijie Yang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005 People’s Republic of China
- The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Qingbiao Li
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005 People’s Republic of China
- The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Ning He
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005 People’s Republic of China
- The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005 People’s Republic of China
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Yu W, Chen Z, Ye H, Liu P, Li Z, Wang Y, Li Q, Yan S, Zhong CJ, He N. Effect of glucose on poly-γ-glutamic acid metabolism in Bacillus licheniformis. Microb Cell Fact 2017; 16:22. [PMID: 28178965 PMCID: PMC5299652 DOI: 10.1186/s12934-017-0642-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 01/28/2017] [Indexed: 11/23/2022] Open
Abstract
Background Poly-gamma-glutamic acid (γ-PGA) is a promising macromolecule with potential as a replacement for chemosynthetic polymers. γ-PGA can be produced by many microorganisms, including Bacillus species. Bacillus licheniformis CGMCC2876 secretes γ-PGA when using glycerol and trisodium citrate as its optimal carbon sources and secretes polysaccharides when using glucose as the sole carbon source. To better understand the metabolic mechanism underlying the secretion of polymeric substances, SWATH was applied to investigate the effect of glucose on the production of polysaccharides and γ-PGA at the proteome level. Results The addition of glucose at 5 or 10 g/L of glucose decreased the γ-PGA concentration by 31.54 or 61.62%, respectively, whereas the polysaccharide concentration increased from 5.2 to 43.47%. Several proteins playing related roles in γ-PGA and polysaccharide synthesis were identified using the SWATH acquisition LC–MS/MS method. CcpA and CcpN co-enhanced glycolysis and suppressed carbon flux into the TCA cycle, consequently slowing glutamic acid synthesis. On the other hand, CcpN cut off the carbon flux from glycerol metabolism and further reduced γ-PGA production. CcpA activated a series of operons (glm and epsA-O) to reallocate the carbon flux to polysaccharide synthesis when glucose was present. The production of γ-PGA was influenced by NrgB, which converted the major nitrogen metabolic flux between NH4+ and glutamate. Conclusion The mechanism by which B. licheniformis regulates two macromolecules was proposed for the first time in this paper. This genetic information will facilitate the engineering of bacteria for practicable strategies for the fermentation of γ-PGA and polysaccharides for diverse applications. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0642-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wencheng Yu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Zhen Chen
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Hong Ye
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Peize Liu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Zhipeng Li
- Fujian Provincial Key Laboratory of Fire Retardant Materials, College of Materials, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Yuanpeng Wang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Qingbiao Li
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Shan Yan
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Chuan-Jian Zhong
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Ning He
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China. .,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China.
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Luo Z, Guo Y, Liu J, Qiu H, Zhao M, Zou W, Li S. Microbial synthesis of poly-γ-glutamic acid: current progress, challenges, and future perspectives. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:134. [PMID: 27366207 PMCID: PMC4928254 DOI: 10.1186/s13068-016-0537-7] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 05/31/2016] [Indexed: 05/22/2023]
Abstract
Poly-γ-glutamic acid (γ-PGA) is a naturally occurring biopolymer made from repeating units of l-glutamic acid, d-glutamic acid, or both. Since some bacteria are capable of vigorous γ-PGA biosynthesis from renewable biomass, γ-PGA is considered a promising bio-based chemical and is already widely used in the food, medical, and wastewater industries due to its biodegradable, non-toxic, and non-immunogenic properties. In this review, we consider the properties, biosynthetic pathway, production strategies, and applications of γ-PGA. Microbial biosynthesis of γ-PGA and the molecular mechanisms regulating production are covered in particular detail. Genetic engineering and optimization of the growth medium, process control, and downstream processing have proved to be effective strategies for lowering the cost of production, as well as manipulating the molecular mass and conformational/enantiomeric properties that facilitate screening of competitive γ-PGA producers. Finally, future prospects of microbial γ-PGA production are discussed in light of recent progress, challenges, and trends in this field.
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Affiliation(s)
- Zhiting Luo
- />College of Light Industry and Food Engineering, Guangxi University, Nanning, 530004 China
| | - Yuan Guo
- />National Engineering Research Center for Non-Food Biorefinery, Guangxi Academy of Sciences, Nanning, 530004 China
| | - Jidong Liu
- />College of Light Industry and Food Engineering, Guangxi University, Nanning, 530004 China
| | - Hua Qiu
- />College of Light Industry and Food Engineering, Guangxi University, Nanning, 530004 China
| | - Mouming Zhao
- />College of Light Industry and Food Engineering, Guangxi University, Nanning, 530004 China
| | - Wei Zou
- />College of Bioengineering, Sichuan University of Science and Engineering, Zigong, 643000 Sichuan China
| | - Shubo Li
- />College of Light Industry and Food Engineering, Guangxi University, Nanning, 530004 China
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