Enzymatic synthesis of γ-L-glutamyl-L-cysteine with immobilized γ-glutamyltranspeptidase

γ-glutamyltranspeptidase (GGT) from B. subtilis NX-2 was immobilized onto Eupergit C250L via oxirane method. The optimal pH and temperature of immobilized GGT were 9.0 and 60 °C. The thermal and storage stability of GGT were significantly increased after immobilization. The activity of remaining GGT was still exceed 80% of its initial activity after storage for 100 d and reused for 20 batches. At the conditions of L-Glutamine 20 mmol/L, S-benzyl-cysteine (S-Bzl-cys) 20 mmol/L, immobilized GGT 0.0375 U/mL and pH 9.0, a maximal product yield of 4.3 mmol/L was obtained after incubated at 40 °C for 22 h, resulting in an increase of 11.96% compared to that use free GGT as catalyst. The protecting group of S-Bzl-γ-L-glutamyl-L-cysteine was removed with trifluoromethanesulfonic acid. The purity of produced γ-L-glutamyl-L-cysteine (GGC) was 94.1%.