Characterization of waste cell biomass derived glutamate decarboxylase for in vitro γ-aminobutyric acid production and value-addition

Waste biomass of Lactobacillus brevis obtained from in vivo γ-aminobutyric acid (GABA) production was used for value-addition. This study aims to extract glutamate decarboxylase (GAD) and characterize it for in vitro GABA production. Extracted GAD showed an excellent activity for in vitro GABA production. 52 W ultrasonic output was best in crude GAD extraction which was purified by Q HP anion-exchange column followed by Superdex-200 colloid separation column. The molecular weight of the purified GAD was determined to be ~53 kDa, and the Km value for L-glutamic acid was calculated ~7.65 mM. Pyridoxal 5′-phosphate (PLP) acted as the best cofactor for GAD. Optimum temperature and PLP dosing were deferring for crude and purified enzyme forms which respectively exhibited at 45°C, 55°C, 200 µmol and 20 µmol whereas optimum pH was the same at 4.5. GAD finds applications in food industries hence its detailed characterization would be promising for commercial exploitations.