发酵条件对嗜热链球菌ST1发酵乳粘度的影响

Effect of cultural conditions on the viscosity of fermented milk by Streptococcus thermophilus ST1

对一株产粘嗜热链球菌ST1的形态进行了观察,探讨了pH、温度、不同碳源和乳清浓缩蛋白(WPC)对嗜热链球菌ST1发酵脱脂乳粘度、酸度的影响。该菌株经活化,在全脂乳固体培养基上培养后、采用结晶紫染色,在显微镜下观察到菌体呈球形或卵形,链状分布,菌体表面没有荚膜。用ST1发酵10%脱脂乳,获得了不同发酵时间下表观粘度和滴定酸度的变化情况,优化出嗜热链球菌ST1发酵脱脂乳产粘的条件为:pH6·5,温度42℃,添加2%(w/v)蔗糖或0·5%(w/v)WPC392。

The morphologic characteristics of a slime-producing strain,Streptococcus thermophilus ST1 were studied.By crystal violet staining,the strain grown on a full-fat milk solid medium was observed by microscopy to be globular or oval without capsules on the bacterial surface,and the bacteria cells were presented in chains.The effects of pH,temperature,supplementation with carbon sources and whey protein concentrate（WPC）on the viscosity of fermented skim milk by S.thermophilus ST1 were studied when the strain was grown in 10% reconstituted skim milk.According to the results of the apparent viscosity and titration acidity of the fermented samples,the optimized cultural conditions for slime production by S.thermophilus ST1 were pH 6.5,temperature 42℃,2%（w/v）sucrose or 0.5%（w/v）WPC392.