Combining Lactiplantibacillus plantarum and Bifidobacterium adolescentis can improve GABA production in faecal fermentations

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 synthesised 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 hours and increased the GABA concentration without causing major disruptions in the microbiome or metabolome. B. 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.