Abstract:

Koumiss, a traditional fermented mare’s milk in Xinjiang province of China, is an abundant source of lactic acid
bacteria. Fourteen strains of lactic acid bacteria from Koumiss were screened for lactose-hydrolyzing ability. A strain of
Lactobacillus fermentum RB-6 with high rate of lactose hydrolysis (37%) was obtained. Single-factor and orthogonal array
designs were used to optimize the inoculum quantity, fermentation temperature, and fermentation time for the selected
strain. The results indicated that when the fermentation was carried out for 8 h with an inoculum size of 3% at 39 ℃, the rate
of lactose hydrolysis was 47%, which was increased by 10% as compared with that before optimization.

Key words: screening, lactose hydrolysis, lactic acid bacteria, fermentation conditions, optimization