Abstract
The effects of pH and L-cysteine HCI on the growth and stability of Biofidobacterium breve were studied. Significantly higher population was obtained by culturing at pH $6.0{\sim}6.5$ than at any other pH. The cultures that had been grown at pH $5.5{\sim}6.0$ were more stable during storage than those grown at other pH. The number of B. breve that had been grown at pH 5.5 and 6.0 remained as $2.4{\times}10^6ml/\;and\;1.4{\times}10^6ml,$ respectively, after 25 days of storage at $4^{\circ}C$. The ${\beta}$-galactosidase activity of B. breve grown at pH 5.5 and 6.0 was reduced only to $78{\sim}85%$ of the control after the same storage condition, whereas the culture grown at pH 7.0 exhibited a signficant decline in population and ${\beta}$-galactosidase activity during $4^{\circ}C$. The growth of B. breve was promoted by 0.05% L-cysteine HCI, and cells grown in MRS with $0.05{\sim}0.10%$ L-cysteine HCI were more resistant to hydrogen peroxide. With respect to the effect to the effect of osmoprotectants on the survival of B. breve subjected to freeze-drying, addition of 2 mM betaine of 2 mM trehalose increased the growth rate of cells grown under osmotic stress and also made the organism more osmotolerant. Furthermore, the betaine or trehalose increased the survivability of the cells after freeze-drying.