Abstract: This experiment studied the optimization of fermentation conditions of the genetically engineered Escherichia coli strain of γ-glutamyltranspeptidase γ-EGT for the biosynthesis of theanine. The significant effects of initial pH, cultivation time and IPTG induction temperature on the activity of γ-GGT were noted with Plackett-Burman design. It then revealed with the method of response surface methodology (RSM) that initial pH 7.32, cultivation time 6.67 h and IPTG induction temperature 31.51 ℃ are optimum for the activity of γ-GGT, with a predicted γ-GGT activity 4.60 U/ml, and the experimentalγ-GGT activity 4.64 U/ml. The yield of theanine from L-Gln and ethylamine is 35.18 g/L.

Key words: theanine； &gamma, -glytamyltranspeptidase (&gamma, -GGT)； Plackett-Burman design； response surface methodology (RSM)；