传统牦牛酸奶中产细菌素乳酸菌的筛选及鉴定

采用溶钙圈法对来自青海海南藏族自治区、四川阿坝、甘孜理塘的牦牛酸奶样品的菌株进行分离筛选，采用形态学观察和16S rRNA序列分析进行鉴定；测定筛选菌株上清液对金黄色葡萄球菌（Staphylococcus aureus）、大肠杆菌（Escherichia coli）抑菌活性；考察筛选菌株上清液对蛋白酶的耐受性及对抗生素的敏感性，并确定细菌素种类。结果表明，共分离筛选出6株菌（编号为A1～A2及G1～G4），其中菌株A1～A2被鉴定为嗜热链球菌（Streptococcus thermophilus），菌株G1～G4被鉴定为屎肠球菌（Enterococcus faecium）；菌株G3对金黄色葡萄球菌、大肠杆菌的抑菌圈直径＞20 mm，且对蛋白酶不耐受，表明该菌株产细菌素，对常见抗生素敏感，经细菌素基因鉴定证实，该菌株产肠球菌素A和肠球菌素P。综上，菌株G3可作为产细菌素益生菌的候选菌株。

Screening and identification of bacteriocin-producing lactic acid bacteria from traditional yak yogurt

The strains in yak yogurt samples from Qinghai Hainan Tibetan Autonomous Region, Sichuan Aba and Ganzi Litang were isolated and screened by calcium dissolving circle method, and identified by morphological observation and 16S rRNA sequence analysis. The antibacterial activity of the supernatant of the screened strain against Staphylococcus aureus and Escherichia coli was determined. The tolerance to protease and the sensitivity to antibiotics of the supernatant of screened strain were investigated, and the bacteriocin species were determined. The results showed that 6 strains (numbered as A1-A2 and G1-G4) were isolated and screened. Among them, strains A1-A2 were identified as Streptococcus thermophilus and strains G1-G4 were identified as Enterococcus faecium. The diameter of inhibition zone of strain G3 to S. aureus and E. coli was more than 20 mm, and the strain was intolerant to protease, indicating that the strain produced bacteriocin and was sensitive to common antibiotics. The bacteriocin gene identification confirmed that the strain produced enterococcus A and enterococcus P. In conclusion, strain G3 could be used as a candidate strain for bacteriocin-producing probiotics.