摘要
Poly-γ-glutamic acid is an extracellular polymeric substance with various applications owing to its valuable properties of biodegradability,flocculating activity,water solubility,and nontoxicity.However,the ability of natural strains to produce poly-γ-glutamic acid is low.Atmospheric and room temperature plasma was applied in this study to conduct mutation breeding of Bacillus licheniformis CGMCC 2876,and a mutant strain M32 with an 11%increase in poly-γ-glutamic acid was obtained.Genome resequencing analysis identified 7 nonsynonymous mutations of ppsC encoding lipopeptide synthetase associated with poly-γ-glutamic acid metabolic pathways.From molecular docking,more binding sites and higher binding energy were speculated between the mutated plipastatin synthase subunit C and glutamate,which might contribute to the higher poly-γ-glutamic acid production.Moreover,the metabolic mechanism analysis revealed that the upregulated amino acids of M32 provided substrates for glutamate and promoted the conversion between L-and D-glutamate acids.In addition,the glycolytic pathway is enhanced,leading to a better capacity for using glucose.The maximum poly-γ-glutamic acid yield of 14.08 g·L^(–1)was finally reached with 30 g·L^(–1)glutamate.
基金
This work was financially supported by the National Natural Science Foundation of China(Grant Nos.32170061 and 31871779).
