Tapping the potential of lactic acid bacteria: optimizing gamma-aminobutyric acid production for enhanced health benefits in fermented milk

Abstract

Gamma-aminobutyric acid (GABA) is a non-protein amino acid with numerous health benefits, such as reducing hypertension, treating diabetes, and providing neuroprotection. GABA can be produced by lactic acid bacteria (LAB), but not all LAB produce GABA. Therefore, it is necessary to screen LAB isolates with the potential to be GABA producers. GABA was analyzed qualitatively using thin-layer chromatography (TLC) and quantitatively by Ultraviolet-visible (UV-Vis) spectrophotometer. Ten LAB isolates were evaluated for their ability to produce GABA. Among these, Pediococcus acidilactici YKP4 produced the highest concentration of GABA. P. acidilactici YKP4 as the highest GABA producer and Lacticaseibacillus rhamnosus BD2 as a probiotic candidate were further studied to increase GABA production in de Man Rogosa Sharpe (MRS) broth by providing monosodium glutamate (MSG) as the precursor and applying different initial pH and incubation time. The highest production of GABA by P. acidilactici YKP4 (3.30±0.03 g/L) was obtained by the addition of 1% MSG while that of L. rhamnosus BD2 (2.67±0.07 g/L) by 2% MSG with initial pH of 5.0 and incubation time of 72 h. Application of both LAB as a starter culture for milk fermentation showed that GABA production in milk was lower than in MRS broth. Enrichment of milk with MSG increased GABA from 1.80±0.03 g/L to 1.94±0.02 g/L in P. acidilactici YKP4 with 1% MSG, and from 1.15±0.03 g/L to 1.33±0.04 g/L in L. rhamnosus BD2 with 2% MSG. Besides, P. acidilactici YKP4 and L. rhamnosus BD2 were considered as potential LAB for GABA production and can be applied to ferment milk as a functional food.