Whole-cell display of Pyrococcus horikoshii glutamate decarboxylase in Escherichia coli for high-titer extracellular gamma-aminobutyric acid production

Abstract

We investigated the effect of cell-surface display of glutamate decarboxylase (GadB) on gamma-aminobutyric acid (GABA) production in recombinant Escherichia coli. We integrated GadB from the hyperthermophilic, anaerobic archaeon Pyrococcus horikoshii to the C-terminus of the E. colt outer membrane protein C (OmpC). After 12 hr of culturing GadB-displaying cells, the GABA concentration in the extracellular medium increased to 3.2 el, which is eight times that obtained with cells expressing GadB in the cytosol. To further enhance GABA production, we increased the temperatures of the culture. At 60 degrees C, the obtained GABA concentration was 4.62 g/I after 12 hr of culture, and 5.35 g/l after 24 hr, which corresponds to a yield of 87.7%.