产PrtS蛋白酶嗜热链球菌的筛选及其生长特性研究

Screening of PrtS protease-producing Streptococcus thermophiles and its growth characteristics

从商业发酵剂中初步分离出8株疑似嗜热链球菌,与实验室保存的26株嗜热链球菌,共收集到34株菌。通过PCR反应获得具有PrtS基因的一株菌,利用FSDA培养基确定该菌株具有PrtS蛋白酶活性,经生理生化实验和16S rDNA序列同源性分析该菌株为嗜热链球菌,命名为Streptococcus thermophiles 922。该菌株在LM17培养基中培养10 h时,活菌数达到9.68 log cfu/mL;在脱脂乳培养基中,产酸速度快,产酸量较高。实验结果为深入探究PrtS蛋白酶对嗜热链球菌生长和发酵性能影响提供基础。

A total of 34 strains were collected, in which 8 suspected strains were isolated from commercial starters and 26 strains of Streptococcus thermophiles were obtained from our laboratory. One strain existed PrtS gene was screened by PCR, and then the PrtS protease activity was determined using FSDA medium. This strain was identified to be Streptococcus thermophiles by physiological and biochemical experiments together with 16S rDNA sequencing, and named Streptococcus thermophiles 922. The growth characteristics were measured. Its viable count reached to 9.68 log cfu/mL in LM17 medium at 10 h of incubation. It also had high acidification rate. The results provided a basis for subsequent experiments about the infuence of PrtS protease on growth and fermentation of Streptococcus thermophiles.