Abstract: The best composition of the culture medium of streptococcus thermophilus is: skimmed milk powder13%, glucose 2%, hydrolyzed milk powder 4%, yeast extract 0. 25%, phosphate buffer 0. 025%mol/L,PH6. 8. It would get Peak strain concentration when streptococcus thermophilus was cultured at 37℃ for 6-8hours. And for lactobacillus bulgaricus, they are: skimmed milk powder 13%, glucose 2%, yeast extract0. 25%, phosphate buffer 0. 05mol/L, PH 6. 8, culture at 42℃ for 6 hours.

Key words: Lactic acid bacteria, Separation