Abstract:

Based on the experiential data on fermentation in 2.5-L stirred fermentor, several experienced methods were used to study the scale-up of Lactobacillus bulgaricus (KLDS 1.9201) and Streptococcus thermophilus (KLDS 3.0201) batch fermentation from flask production to bench production. The scale-up fermentation of yoghurt strains from 2.5-L to 15-L fermentor could be successfully conducted when the agitation rate ranged from 50 r/min to 80 r/min and the dissolved oxygen concentration was lower than 5%. The maximum lactose consumption and lactic acid concentration for Lactobacillus delbrueckii subsp. Bulgaricus KLDS 1.9201 reached 80.3% and 49 g/L respectively, and the living bacterial number attained 2.2×109 CFU/ml after the growth for 12 h. The maximum lactose utilization and lactic acid concentration for Streptococcus sativarius subsp thermophilus KLDS 3.0201 reached 80.2% and 39 g/L, respectively, and the living bacterial number attained 4.9×109 CFU/ml after the growth for 8 h.

Key words: yoghurt strains, batch fermentation, scale-up fermentation