Cell surface display of Neurospora crassa glutamate decarboxylase on Escherichia coli for extracellular Gamma-aminobutyric acid production from high cell density culture

Abstract

GABA is produced from the decarboxylation of glutamate by glutamate decarboxylase enzyme (GadB). Various hetrologous GadB enzymes has been indentified and introduced in Escherichia coli to improve the productivity of GABA. In this study, cell surface display strategy was employed by displaying Neurospora crassa glutamate decarboxylase (GadB) on the surface of Escherichia coli using OmpC as an anchoring motif. To construct the display system, the GadB was fused to truncated C-terminus of OmpC and expressed in E. coli. The recombinant E. coli displaying GadB has produced 3.03 g/L of GABA from 10 g/L glutamate within 12 h of culture period. When the GadB display system was cultured at high cell density, 100% GABA yeild was achieved from 50 g/L of glutamate. The results suggest that the GadB expression on the E. coli surface is stable and effective on GABA production. The surface display strategy can be applied on other potential enzyme candidates and used in Industry for bulk chemical production.