Gamma-aminobutyric acid (GABA) is a building block to synthesize 2-pyrrolidone and biodegradable polyamide 4.However, high costs of the production and purification process is the major obstacles for the wide application of GABA.Therefore, we developed an efficient process to increase GABA production at a low cost using a recombinant Escherichia coli expressing glutamate decarboxylase.Codon optimization of gadB genes from E.coli, Lactobacillus brevis, Lactococcus lactis and Lactobacillus plantarum were expressed to produce GABA in E.coli BW25113.The gadB gene from L.lactis had the highest GABA production.Recombinant E.coli, as a whole-cell biocatalysts, was suspended in various optical densities and substrate concentrations at different temperatures to determine the optimum conditions for GABA production.The highest final GABA concentration, 309.3 ± 2.7 g/L, was obtained from 3 M L-glutamic acid (Glu) with a conversion yield of 99.9% and a productivity of 38.6 g GABA/L/h at 45 ℃.Furthermore, the engineered strain could be used for at least 3 cycles in 2 M Glu with a conversion rate above 99.3% and a productivity above 41 g/L/h.This is a cost-effective process for GABA production with potential applications in large-scale industrial production.