Improving the growth and stability following of lyophilized Bifidobacterium breve M4A and Bifidobacterium longum subsp. longum FA1 in skimmed milk media

Abstract

Among commensal bacteria, Bifidobacteria are one of the most numerous probiotics in the mammalian gut. Two strains of Bifidobacterium (B) were isolated from stool of breastfed infants and identified by their 16S rRNA genes. The strains were identical to B. longum subsp. longum FA1 and B. breve M4A. These isolates were conserved by lyophilisation, and the survival rates measured six months after lyophilisation, were 74.74% and 99.6% for B. longum subsp. longum FA1 and B. breve M4A, respectively. To improve the survival rate in skimmed milk media used for lyophilisation, the skimmed milk was supplemented with yeast extract, glucose and oligofructose. Supplementation decreased the doubling time and increased the viable cell count. Statistical analyses showed a nonlinear relationship between skimmed milk media and bacterial count number and acid production, which indicates an opposite impact of yeast extract with glucose or oligofructose supplementation in skimmed milk media. Response surface plots were applied to optimize the supplemented skimmed milk media. Both strains grew more rapidly in supplemented media than in skimmed milk-based medium alone. Acid production was higher in B. breve M4A than B. longum subsp. longum FA1 when inoculated into skimmed milk supplemented with yeast extract, glucose, and oligofructose. The fermentation ability in skimmed milk was dependent on nutrient availability and the carbon source, which decreased the doubling time and increased the viable cell count. The addition of yeast extract, glucose, and oligofructose to skimmed milk increased the growth rate and acid production, compared with skimmed milk alone, when incubated anaerobically at 37°C for 48 h. The purpose of this study was to evaluate the potential synergy between Bifidobacterium isolates with yeast extract, glucose, and oligofructose in skimmed milk after 6 months of conservation.