Abstract: The growing properties of two excellent yogurt fermentation strains were studied in this paper. The results showed that the optimum carbon and nitrogen sources were lactose and peptone respectively, Zn2+ and Mg2+ could promote the growth of the strains. For adding Ca2+, only E2 could be promoted. The optimum culture conditions of E2 were as follows: temperature 41℃, the initial pH 8, culture for 3.5 h, inoculation volume 2%; the optimum culture conditions of D2 were as follows: temperature 43℃, the initial pH 7, culture for 2.5 h,inoculation volume 4%．

Key words: yogurt fermentation strains, medium optimization, growth curve