Enzymatic production of L-alanyl-L-glutamine by recombinant E. coli expressing α-amino acid ester acyltransferase from Sphingobacterium siyangensis

An enzymatic production method for synthesizing L-alanyl-L-glutamine (Ala-Gln) from L-alanine methyl ester hydrochloride (AlaOMe) and L-glutamine (Gln) was developed in this study. The cultivation conditions for an Escherichia coli strain overexpressing α-amino acid ester Acyltransferase from Sphingobacterium siyangensis AJ 2458 (SAET) and reaction conditions for Ala-Gln production were optimized. A high cell density culture broth prepared by fed-batch cultivation showed 440 units/mL of Ala-Gln-producing activity. In addition, an Ala-Gln-producing reaction using intact E. coli cells overexpressing SAET under optimum conditions was conducted. A total Ala-Gln yield of 69.7 g/L was produced in 40 min. The molar yield was 67% against both AlaOMe and Gln.