Enterococcus avium from a traditional Chinese liquor fermentation system with the potential for the de novo synthesis of GABA

Abstract

γ-Aminobutyric acid (GABA) is a prevalent nonprotein amino acid with diverse physiological functions, attracting considerable interest in the food industry. However, current GABA-producing strains require glutamate as a substrate for synthesis. Probiotics capable of de novo GABA synthesis using sugars without glutamate are crucial for developing novel foods. This study employed a pH indicator method to selectively screen for GABA-producing bacteria. Nineteen strains with fermentation liquid pH greater than 5 were obtained, all demonstrated the ability to synthesize GABA from Daqu. Among these strains, Enterococcus (E.) avium GL1 stood out for its high GABA production capacity, reaching 9.8 g/L when utilizing glucose for de novo GABA synthesis without monosodium glutamate (MSG). E. avium GL1 exhibited robust viability in challenging environments, maintaining stability in simulated gastric and intestinal fluids. As a potentially probiotic strain, E. avium GL1 achieved remarkable GABA production of 206.84 g/L with a production efficiency of 2.87 g/L/h, facilitated by automatic pH control during fermentation through continuous addition of glucose and MSG addition. This exceptional result represents the highest GABA production reported for E. avium, highlighting its significant potential for the development of innovative functional foods.