Oat-based beverage biofortification with the novel riboflavin-overproducing and dextran-producing Leuconostoc...

During fermentation, incorporation of food grade lactic acid bacteria that synthesize functional metabolites, such as vitamins, prebiotics, and bioactive compounds is an efficient strategy for in situ biofortification of food. In this study, exposure of the dextran-producer Leuconostoc mesenteroides B12 to roseoflavin (300 μg) resulted in the selection of the riboflavin-overproducing B12-B2 strain, which produced high levels of riboflavin (vitamin B₂) (1.5 mg/L) and dextran (2.92 g/L) in a synthetic medium. During fermentation of a commercial oat-based beverage over 24 h, B12-B2 exhibited good cell growth (up to 3.16 × 10¹¹ CFU/mL), together with high metabolic activity, acidification capability (42.4°D) and high CO₂ production (26 mM). Moreover, B12-B2 efficiently produced riboflavin (0.57 mg/L), dextran (5.32 mM), mannitol (79.21 mM), lactic acid (29.98 mM) and the prebiotic oligosaccharide panose (13.39 mM). The dynamic viscosity of the oat-based beverage increased significantly during fermentation with B12-B2 (to approximately 305.5 mPa·s). The ability to reduce pH values and influence in cell viability was confirmed after a storage period of 28 days. The present study highlights, for the first time, the potential of L. mesenteroides for the biofortification of plant-based beverages, a product category in which this species has not previously been employed as a starter or additive culture.