title: Physiological and metabolic analysis of nitrate reduction on poly-gamma-glutamic acid synthesis in Bacillus licheniformis WX-02.
abstract: Nitrate is an important nitrogen source for organism, but whether and how nitrate improves poly-γ-glutamic acid (γ-PGA) production of bacterial is not clear. The effect of nitrate on γ-PGA production of Bacillus licheniformis WX-02 was investigated. By addition of 50 mmol/L nitrate, the γ-PGA yield reached 12.3 ± 0.21 g/L, which increased 2.3-fold compared to the control. The mechanism of enhanced γ-PGA production was further investigated by analysis of nitrate reduction, physiology, pyruvate overflow metabolism and energy synthesis. Nitrate reduction was only carried out in the middle stage of γ-PGA fermentation. The result of consumption of nutrients showed that glucose uptake was not effected and the L-glutamic acid utilization efficiency increased from 48.3 to 77.0 %. The date of overflow metabolism obtained from high-performance liquid chromatography showed that the metabolism of pyruvate, formate, lactate and acetoin was both heightened by nitrate reduction, while the 2,3-butanediol biosynthesis was decreased. Meanwhile, the change of energy indicated that more ATP was synthesized during nitrate reduction. In summary, nitrate was a positive effector of γ-PGA biosynthesis in B. licheniformis WX-02 and nitrate reduction affected multi-metabolism pathways, including glycolysis, overflow metabolism and energy metabolism.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China, lixin0807@gmail.com.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Xiangyong
authors.initials: X
authors.lastname: Gou
authors.forename: Dan
authors.initials: D
authors.lastname: Long
authors.forename: Zhixia
authors.initials: Z
authors.lastname: Ji
authors.forename: Lifang
authors.initials: L
authors.lastname: Hu
authors.forename: Dihong
authors.initials: D
authors.lastname: Xu
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Shouwen
authors.initials: S
authors.lastname: Chen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001407:Bacillus / Q000187:drug effects / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000378:metabolism* / Q000494:pharmacology; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis
chemical_list: D009566:Nitrates; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D000255:Adenosine Triphosphate