Ropy exopolysaccharide-producing Bifidobacterium longum YS108R as a starter culture for fermented milk

Bifidobacteria are generally inferior compared to traditional starter lactic acid bacteria (LAB) in terms of fermentation properties. The results of this study showed that the use of a ropy EPS producing strain Bifidobacterium longumYS108R during fermentation improved the physicochemical properties of fermented milk, including decreased whey syneresis and increased water-holding capacity and apparent viscosity, however, another non-ropy EPS producing strain B. longum C11A10B did not exert such effects. Furthermore, we found that synergistically fermented milk with YS108R and commercial starter could reduce the production of acetic acid, a metabolite of bifidobacteria, and scored better in terms of sensory evaluation, especially with regards to mouthfeel texture. Comparative genomic analysis revealed a single mutation in the protein-tyrosine kinase gene of strain YS108R, which may relate to ropy phenotype. Our results indicate that ropy-EPS producing B. longumYS108R is suitable as an adjunct culture for the manufacture of novel fermented dairy products.