摘要
大肠杆菌(Escherichia coli)产生的β-葡糖苷酸酶可以分解4-甲基伞形酮酰β-D-葡糖醛酸苷(4-MUG),形成产生荧光的终产物:4-甲基伞形酮,本试验将4-MUG加入牛奶中并应用荧光扫描仪检测酶解终产物的荧光强度以判断大肠杆菌在牛奶中的生长状况.试验结果表明,荧光强度自第4小时起开始上升,滞后于活菌数的增加,但荧光度增强与活菌数增加具有较好的一致性,而且方法快速,简便,应用荧光分析法初步证明乳酸菌对大肠杆菌的生长未见有抑制作用.
Escherichia coli could produce β-glucuronidase during its growth in the culture media. This enzyme cleaves the substrate, 4-metliylumbelliferyl-β-D-glucuronide (4-MUG), to yield a fluorogenic end product. This experiment was aimed to assess the growth of E. coli in the 4-MUG incorporated milk samples by determining fluorescence of the enzymatic end product with the Fluoroscan. Fluorescence was observed to increse slightly at the first few hours of incubation and markedly after hour 6. The fluorescence curve had a pattern similar to the increase of viable bacterial cells although there was a delayed appearance of fluorescence at the frist few hours of incubation. It was also found that lactic acid bacteria were unable to inhibit the growth of E. coli as assayed with the fluorometric method.
基金
国际科学基金会(IFS)资助项目
关键词
牛奶
大肠杆菌
荧光测定法
milk
fluorometry
Escherichia coli
β-glucuronidase
