1. Introduction
Gamma-aminobutyric acid (GABA) is a non-proteinaceous amino acid widely used in the food and pharmaceutical industry, where it serves as an inhibitor of neurotransmission with hypotensive and diuretic effects [1–4], as well as in the chemical industry, where it can be employed as a precursor for biodegradable polymers as an intermediate to pyrrolidone to synthesize polymer Nylon 4 [5,6]. The bioconversion of GABA is undergone with glutamate decarboxylase (GAD, EC 4.1.1.15), which catalyzes the GABA conversion from glutamate, while producing CO2 [7].