Performances of new isolates of Bifidobacterium on fermentation of soymilk.

Growth and metabolic activity of several new, human origin isolates of Bifidobacterium strains were investigated. All tested bifidobacteria strains were grown well on the native soymilk medium without any additional nutrients. The fermentation processes cultured with initial cell concentrations in 10⁵ -10⁷ cfu/ml resulted in 10⁸ cfu/ml after 8-12 h of incubation in soymilk, and were kept viable up to the end of fermentation (48 h). Volumetric productivities of B. bifidum B3.2, B. bifidum B7.1 and B. breve B9.14 were 1.6 × 10¹⁰ cfu/L.h, 4.5 × 10¹⁰ cfu/L.h and 7.6 × 10⁹ cfu/L.h, respectively, whereas these values of B. lactis Bb-12 and B. longum Bb-46 probiotic strains were 2.7 × 10⁹ cfu/L.h and 1.0 x 10¹⁰ cfu/L.h. The α-galactosidase activities were also detected in the intracellular fraction of the disrupted cells. Productions of lactic and acetic acids were in the range of 23-60 mmol/L and 2.4-5.6 mmol/L, respectively. Molar ratios of acetate to lactate in all tested strains varied from 0.05-0.1 that are very promising for further technological development of probiotic fermented soy-based food products.