GABA- and riboflavin-enriched soy and oat beverages using selected lactic acid bacteria

Abstract

Gamma-aminobutyric acid (GABA) and riboflavin have received significant attention as attractive bioactive compounds with attributed health-promoting properties, including antidepressant and neuroprotective effects. This study aimed to develop soy and oat beverages enriched in GABA and riboflavin through fermentation with specific lactic acid bacteria (LAB) strains. The screening of LAB producers of bioactive compounds concluded with the identification of new riboflavin-producing LAB strains, including for the first time the species Fructobacillus tropaeoli. Nevertheless, since spontaneous strains resistant to roseoflavin showed the ability to overproduce riboflavin, four mutants of Lactiplantibacillus plantarum and Limosilactobacillus fermentum were selected. Additionally, four strains belonging to the species L. plantarum and Lactococcus lactis were selected as high GABA producers. Soy and oat beverages supplemented with 0.2 % monosodium glutamate, as precursor of GABA, and inoculated with the selected single strains were fermented for 48 h at their optimal temperature (30 °C or 37 °C). Riboflavin and GABA production, as well as glutamate utilization, were determined after fermentation, leading to the selection of the riboflavin-overproducing mutant L. plantarum Al03R3 and GABA-producing L. lactis INIA Z174 for co-culture. Fermentation with this combination of strains produced fermented soy and oat beverages enriched with both GABA and riboflavin. Notably, the oat beverage exhibited particularly high yields, reaching 0.98 g/L of GABA and 4.72 mg/L of riboflavin, making it a suitable functional drink for delivering these health-promoting compounds.