Screening, characterization and growth of γ-aminobutyric acid-producing probiotic candidates from food origin under simulated colonic conditions

Aims: This study aims to isolate probiotic bacteria candidates from various starter cultures and fermented foods and characterize their ability to produce γ-aminobutyric acid (GABA). GABA is a major inhibitory neuromediator of the central and enteric nervous systems with a role in several health disorders.

Methods and results: Fourteen strains of lactic acid bacteria were isolated from food environment and screened for the presence of the glutamate decarboxylase (gadB) gene using PCR and GAD enzymatic assay. The identified potent GABA-producers included Strep. thermophilus, Lactiplantibacillus plantarum and Lact. delbrueckii subsp. bulgaricus. GC-FID analyses confirmed the high GABA production capacity of Strep. thermophilus ST16 (1641.5 ± 154.15 μmol l^-1 ), Strep. thermophilus ST8 (1724.5 ± 48.08 μmol/L). To a lesser extent, Bif. animalis ST20, Lact. acidophilus LP16-2 and Ent. faecium ST3 produced 947.5 ± 70.71, 918.0 ± 121.42, and 907.83 ± 55.15 μmol/L of GABA, respectively. These potent strains were able to grow and produce GABA in MRS broth and pre-fermented Macfarlane broth, the latter medium mimicking the nutrient and metabolome composition encountered in the colon. The identified bioactive strains exhibited strong biological safety and probiotic potential profiles as indicated by sensitivity to antibiotics, absence of virulence factors and survival in gastrointestinal conditions.

Conclusions: Several GABA producing probiotic candidates, including Bif. animals ST20, Strep. thermophilus ST8, Lact. acidophilus LP16-2, L. plantarum LP6 & LP9, and Ent. faecium ST3, have shown potential to grow under simulated colonic conditions.

Significance and impact of study: Findings from this study provide evidence of the suitability of the isolated GABA-producing probiotic candidates for the development of health-oriented functional food products.