Overproduction of a γ-glutamyltranspeptidase from Bacillus amyloliquefaciens in Bacillus subtilis through medium optimization

Abstract

γ-Glutamyltranspeptidase (GGT, EC 2.3.2.2) transfers γ-glutamyl moiety from glutamine to amino acids or peptides and hydrolyzes glutamine to glutamate and ammonia. In order to overproduce γ-glutamyltranspeptidase from Bacillus amyloliquefaciens (BAGGT), the encoding gene was cloned and expressed in Bacillus subtilis. The productivity of BAGGT in Bacillus subtilis was improved by 42-fold by using a dual-promoter system that was generated by combining promoters from B. subtilis α-amylase and BAGGT genes. Through optimization of medium composition by Plackett-Burman design and central composition design, BAGGT was produced at 18.3×107 U/L of culture in the optimized medium. Compared to previously used Luria-Bertani medium, the optimized culture medium (15 g/L molasses, 60 g/L corn steep liquor, 6 g/L yeast extract, 4 g/L NaCl, 6 g/L K2HPO4, and 2 g/L KH2PO4), resulted in a 4.3-fold increase in production of BAGGT. © The Korean Society of Food Science and Technology.