title: Extracellular expression of glutamate decarboxylase B in Escherichia coli to improve gamma-aminobutyric acid production.
abstract: Escherichia coli overexpressing glutamate decarboxylase GadB can produce gamma-aminobutyric acid with addition of monosodium glutamate. The yield and productivity of gamma-aminobutyric acid might be significantly improved if the overexpressed GadB in E. coli cells can be excreted outside, where it can directly transforms monosodium glutamate to gamma-aminobutyric acid. In this study, GadB was fused to signal peptides TorA or PelB, respectively, and overexpressed in E. coli BL21(DE3). It was found that TorA could facilitate GadB secretion much better than PelB. Conditions for GadB secretion and gamma-aminobutyric acid production were optimized in E. coli BL21(DE3)/pET20b-torA-gadB, leading the secretion of more than half of the overexpressed GadB. Fed-batch fermentation for GadB expression and gamma-aminobutyric acid production of BL21(DE3)/pET20b-torA-gadB was sequentially performed in one fermenter; 264.4 and 313.1 g/L gamma-aminobutyric acid were obtained with addition of monosodium glutamate after 36 and 72 h, respectively.
authors.affiliation: School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Anqi
authors.initials: A
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: School of Biotechnology, Jiangnan University, Wuxi, 214122, China. xwang@jiangnan.edu.cn.|State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China. xwang@jiangnan.edu.cn.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China. xwang@jiangnan.edu.cn.
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Wang
keywords: Escherichia coli; GadB; Gamma-aminobutyric acid; Glutamate decarboxylase; Secretory expression; TorA