Whole-cell conversion of L-glutamic acid into gamma-aminobutyric acid by metabolically engineered Escherichia coli

A simple and high efficient way for the synthesis of gamma-aminobutyric acid (GABA) was developed by using engineered Escherichia coli as whole-cell biocatalyst from L-glutamic acid (L-Glu). Codon optimization of Lactococcus lactis GadB showed the best performance on GABA production when middle copy-number plasmid was used as expression vector in E. coli BW25113. The highest production of GABA reached 308.96 g L-1 with 99.9 mol% conversion within 12 h, when E. coli Delta gabAB (pRB-lgadB) concentrated to an OD600 of 15 in 3 M L-Glu at 45 degrees C. Furthermore, the strain could be reused at least three cycles in 2 M crude L-Glu with an average productivity of 40.94 g L-1 h(-1). The total GABA yield reached 614.15 g L-1 with a molar yield over 99 %, which represented the highest GABA production ever reported. The whole-cell bioconversion system allowed us to achieve a promising cost-effective resource for GABA in industrial application.