Rihua Xu, Melinda J. Mayer, Mark Philo, Gwénaëlle Le Gall, Guesh Mulaw, Alise J. Ponsero, Arjan Narbad
AIMS: This project aimed to investigate production of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) from potential probiotic strains. We studied production in co-cultures and faecal fermentations and examined the effect of selected strains on the faecal microbiome composition and metabolome in vitro. METHODS AND RESULTS: Strains of intestinally derived Bifidobacterium adolescentis and Lactiplantibacillus plantarum from fermented cereals were grown singly, in co-culture and in faecal fermentations designed to simulate colonic conditions. Isolates synthesized varying amounts of GABA in vitro; GABA production could be increased by co-culture, lactic acid, or reduced pH but was decreased in the presence of high buffering. In faecal fermentations, selected strains inoculated singly or in combination persisted over 24 h and increased the GABA concentration without causing major disruptions in the microbiome or metabolome. Bifidobacterium adolescentis supplementation increased short-chain fatty acids acetate and propionate, and L. plantarum was associated with increased succinate levels, while all treatments exhibited a reduction in Escherichia compared to the controls. CONCLUSIONS: GABA production from these lactic acid bacteria is strain-specific and the combination of these two species shows potential for future next-generation probiotic development.