Enrichment of γ-aminobutyric acid (GABA) in a legume-based beverage through the fermentation by Lactiplantibacillus plantarum

In humans, γ-aminobutyric acid (GABA) is recognized as the primary inhibitory neurotransmitter in the central nervous system and covers various others physiological functions such as antioxidant, anti-inflammatory, and antihypertensive activities, as well as positive regulation of anxiety and depression. GABA is also produced by several microorganisms, including lactic acid bacteria (LAB) which, widely used as multifunctional starter cultures to enrich fermented foods with functional properties. Thus, the aim of this study was to screen a collection of 20 Lactiplantibacillus plantarum strains, isolated from fermented foods, for their ability to produce GABA in vitro and in situ during a lab-scale fermentation aimed at producing a legume-based beverage. Initially, optimization of the culture conditions was performed considering parameters such as time and temperature (30 °C for 96 h) for growth and concentration of monosodium glutamate (0, 25, 50, 160, 270 and 400 mM), used by LAB as GABA precursor, by combining colorimetric, GABase enzymatic assay and UPLC/MS-MS analysis. Based on the results, 4 strains (C9S2, C9O4, LAB62 and LT52) were selected and combined as starters to produce a legume-based beverage naturally enriched with GABA. UPLC/MS-MS analyses showed a clear strain-specific GABA production both in vitro (C9S2, 2262.21 ± 219.4 mg/L; LAB62, 790.1 ± 9.5 mg/L; C9O4, 500.7 ± 29.0 mg/L; LT52, 408.7 ± 26.9 mg/L) and in the real food system during the lab-scale fermentation (C1, 6.98 ± 0.03 mg/L; C2, 6.92 ± 0.02 mg/L).