title: The main byproducts and metabolic flux profiling of γ-PGA-producing strain B. subtilis ZJU-7 under different pH values.
abstract: Poly-γ-glutamic acid (γ-PGA) is an extracellular anionic polymer with many potential applications. Although microbial fermentation is the common approach to produce γ-PGA, the broth at the latter stage usually becomes very viscous and severely influences the metabolites producing pattern of target microbe. In this study, acetoin and 2,3-butanediol were confirmed to be the main byproducts of γ-PGA-producing strain B. subtilis ZJU-7 (B. subtilis CGMCC1250), and their effects on the cell growth and γ-PGA biosynthesis were further investigated in shake flasks. The outcome indicated that both acetoin and 2,3-butanediol showed clear impairment on γ-PGA production of B. subtilis ZJU-7. Moreover, the extracellular metabolites profiles of fermentation under three different pH values were acquired and the metabolic flux redistribution of pathways related to γ-PGA biosynthesis was calculated based on the collected data. As a result, the metabolic flux favored to distribute toward glycolytic pathway at pH 6.5, in which the ingestion rate of extracellular glutamic acid was higher and the subsequent γ-PGA biosynthesis was enhanced. The present work provided us a deep insight into the metabolic flux control of γ-PGA biosynthesis, which will stimulate some novel metabolic engineering strategies to improve the productivity of γ-PGA in future.
authors.affiliation: Key Laboratory of Biomass Chemical Engineering (Ministry of Education), Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhu
authors.forename: Jin
authors.initials: J
authors.lastname: Cai
authors.forename: Xiangting
authors.initials: X
authors.lastname: Wu
authors.forename: Jin
authors.initials: J
authors.lastname: Huang
authors.forename: Lei
authors.initials: L
authors.lastname: Huang
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Zhu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zheng
authors.forename: Peilin
authors.initials: P
authors.lastname: Cen
authors.forename: Zhinan
authors.initials: Z
authors.lastname: Xu
mesh_terms: D000093:Acetoin / Q000032:analysis / Q000378:metabolism*; D001412:Bacillus subtilis / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology; D001709:Biotechnology; D002072:Butylene Glycols / Q000032:analysis / Q000378:metabolism*; D057486:Carbon Cycle; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D060847:Metabolic Engineering; D053858:Metabolic Networks and Pathways; D055442:Metabolome; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D002072:Butylene Glycols; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; C026978:2,3-butylene glycol; D000093:Acetoin