This study deals with the utilization of agro-industrial wastes created by barley and wheat bran in the production of a value-added product, γ-aminobutyric acid (GABA). The simple and eco-friendly reaction requires no pretreatment or microbial fermentation steps but uses barley or wheat bran as an enzyme source, glutamate as a substrate, and pyridoxal 5’-phosphate (PLP) as a cofactor. The optimal reaction conditions were determined on the basis of the temperatures and times used for the decarboxylation reactions and the initial concentrations of barley or wheat bran, glutamate, and PLP. The optimal reactions produced 9.2 mM of GABA from 10 mM glutamate, yielding a 92% GABA conversion rate, when barley bran was used and 6.0 mM of GABA from 10 mM glutamate, yielding a 60% GABA conversion rate, when wheat bran was used. The results imply that barley bran is more efficient than wheat bran in the production of GABA.
γ-Aminobutyric acid (GABA) has a variety of well-known physiological functions, and functional foods containing GABA have been intensively investigated and produced. GABA is a nonprotein amino acid that is synthesized by decarboxylation of glutamate via the enzyme glutamate decarboxylase. The aim of this study was to use barley bran or wheat bran as an enzyme source in the production of GABA, a value-added product, via a simple and eco-friendly reaction. Such a process could make a practical contribution toward improving the bioavailability of GABA as a bioactive ingredient in functional foods. Our results indicate that agro-industrial wastes can be used to produce GABA and that the utilization of agro-industrial wastes to produce bioactive ingredients can subsequently improve their economic value.