Optimization of fermentation for gamma-aminobutyric acid (GABA) production by Lactiplantibacillus plantarum Lp3 and the development of fermented soymilk

Gamma-aminobutyric acid (GABA) yield was taken as the index to optimize the fermentation medium and conditions for Lactiplantibacillus plantarum Lp3, and then fermented soymilk with high GABA yield by L. plantarum Lp3 was developed. GABA is a non-protein amino acid with multiple physiological functions. In recent years, L. plantarum strains have been involved in the metabolism of GABA and can serve as microbials for producing GABA. In this study, the medium and fermentation conditions for the production of GABA by L. plantarum Lp3 were optimized using response surface methodology (RSM). The results showed that the optimal concentrations of glucose, yeast extract, and Ca2+ were 20.20, 15.80, and 9.90 mg/mL, respectively, sodium glutamate was 5.00 mg/mL, fermentation temperature was 35 °C, initial pH was 6.4, and fermentation time was 46 h. Under the optimized conditions, the highest GABA yield was 3.74 mg/mL. In addition, the optimal fermentation conditions of fermented soymilk with high GABA yield by L. plantarum Lp3 were: L. plantarum Lp3 and Streptococcus thermophilus 2:1, sodium glutamate 0.4%, fermentation time 10 h, fermentation temperature 35 °C, and the final GABA yield was 0.552 mg/mL.