Effect of amino acid and milk composite culture on the growth of Streptococcus thermophilus

18 kinds of amino acid were selected to mix with milk respectively to constitute composite medium where Streptococcus thermophilus bacteria were cultured.The results manifested that glutamate,glycine,serine and leucine significantly promoted cell growth of Streptococcus thermophilus when mixed with milk,the viable counts of Streptococcus thermophilus got to 3.80×109 cfu/mL,2.60×109 cfu/mL,2.50×109 cfu/mL and 1.80×109 cfu/mL(Streptococcus thermophilus in antitheses sample was 7.20×108 cfu/mL).Other 14 kinds of amino acid did not promote the growth of ST ideally.With regard to glutamate which had ideal effect on cell growth of Streptococcus thermophilus,the best viable count was raised to 4.80×109 cfu/mL when its content was 10 mg/L.The growth pattern of Streptococcus thermophilus when cultured in the glutamate-milk composite medium was also discussed.