Sharpe broth

Enterococcus faecalis M157 was grown in de Man, Rogosa, and Sharpe broth (Neogen) at 37°C for 24 h. Whey powder was obtained from Samik Dairy and Food Co. Ltd., and 3 g of whey powder was suspended in 27 mL of distilled water. To avoid bacterial contamination, the whey suspension was immersed in a water bath at 80°C for 1 min. During pasteurization, the whey suspension was gently rotated several times. Bacterial contamination was determined by plating on nutrient agar. The whey suspension was then inoculated with E. faecalis M157 and incubated at 37°C for 24 h. After the incubation, the whey suspension was filtered to remove bacteria and the cell-free supernatants were obtained, evaporated, and dried using a spray dryer Buchi) . The whey fermented by E. faecalis M157 (M157-W; 1 mg) was resuspended in 1 mL of distilled water, centrifuged, and the supernatant was collected and adjusted to pH 6.5 with 1 N NaOH. M157-W was filtered using a 0.2-μm syringe filter and stored at -80°C until used.

Two W. cibaria strains, W. cibaria KI 32 and W. cibaria KI 35, were used for biotransformation of whey. Briefly, W. cibaria strains were grown in De Man, Rogosa and Sharpe broth (Neogen) at 37°C for 18 h. For preparing the medium for whey biotransformation, whey powder (Samik Dairy and Food Co. Ltd.) was suspended in distilled water (10%, vol/vol) and pasteurized at 80°C for 1 min. The biotransformation medium was inoculated with W. cibaria (1%) and incubated at 37°C for 24 h. After incubation, cell-free supernatants were collected and evaporated at 40°C in a rotary evaporator (R-300, Buchi) and subsequently dried using a spray dryer (B-290, Buchi). After dryness, whey biotransformed by W. cibaria KI 32 (KI 32-W) and W. cibaria KI 35 (KI 35-W) was resuspended in distilled water. The supernatants were collected after centrifugation at 7,600 × g for 10 min, pH was adjusted to 6.5 using 1 N NaOH, and the supernatants were subsequently filtered using a syringe filter (0.2 μm).