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


CONCLUSIONS
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.
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.
Wencheng
W
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
Z
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
H
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
P
Liu
Fujian Provincial Key Laboratory of Fire Retardant Materials, College of Materials, Xiamen University, Xiamen, 361005, People's Republic of China.
Zhipeng
Z
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.
Yuanpeng
Y
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
Q
Li
Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA.
Shan
S
Yan
Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA.
Chuan-Jian
CJ
Zhong
Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China. hening@xmu.edu.cn.|The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, People's Republic of China. hening@xmu.edu.cn.
Ning
N
He
D000069976:Bacillus licheniformis / Q000235:genetics / Q000378:metabolism*; D002952:Citric Acid Cycle / Q000502:physiology; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D006019:Glycolysis; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D020543:Proteome / Q000378:metabolism; D040901:Proteomics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D011135:Polysaccharides, Bacterial; D020543:Proteome; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D005947:Glucose; D005990:Glycerol
B. licheniformis; Carbon control protein; Glucose; Polysaccharide; γ-PGA