Effect of glucose on poly-γ-glutamic acid metabolism in Bacillus licheniformis

Microbial Cell Factories

Research

Hong Ye¹  Qingbiao Li¹  Wencheng Yu¹  Zhen Chen¹  Yuanpeng Wang¹  Ning He¹  Peize Liu¹  Chuan-jian Zhong²  Shan Yan²  Zhipeng Li³ 

[1] Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, 361005, Xiamen, People’s Republic of China;The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, 361005, Xiamen, People’s Republic of China;Department of Chemistry, State University of New York at Binghamton, 13902, Binghamton, NY, USA;Fujian Provincial Key Laboratory of Fire Retardant Materials, College of Materials, Xiamen University, 361005, Xiamen, People’s Republic of China;

关键词: Glucose;    γ-PGA;    Polysaccharide;    Carbon control protein;    B. licheniformis;   

DOI  :  10.1186/s12934-017-0642-8

 received in 2016-09-06, accepted in 2017-01-28,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundPoly-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.ResultsThe 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.ConclusionThe 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.

【 授权许可】

CC BY   
© The Author(s) 2017