乳链球菌素最小抑菌浓度(MIC)测定及理化性质分析

金黄色葡萄球菌是一种常见的食品致病菌,能引起严重的感染。乳链球菌素(nisin)是世界卫生组织公认的天然食品防腐剂。采用二倍梯度稀释法探究nisin对金黄葡萄球菌的最小抑菌浓度(MIC),通过琼脂平板扩散法分析nisin的理化性质。结果表明,nisin对金黄色葡萄球菌的最小抑菌浓度为2.34μg/mL。理化性质分析发现,nisin在pH为2~6状态下,抑菌效果好,在pH7~11抑菌活性逐渐减弱。Nisin在100℃以下热处理,活性保持良好,120℃处理仍有部分活性,说明其耐热稳定性好。胰蛋白酶、木瓜蛋白酶、蛋白酶K处理nisin,抑菌活性均有一定的削弱,其中蛋白酶K削弱最为明显。Triton-100、Tween20表面活性剂对nisin抑菌活性有细微的协同作用,但SDS可明显抑制其抑菌活性。

Nisin minimum inhibitory concentration(MIC)determination and its physicochemical property

Staphylococcus aureus is a common food pathogen which can cause serious infections to human.Nisin was recognized by the World Health Organization as a natural food preservative.The study was to investigate the minimum inhibitory concentration(MIC)of Nisin against S.aureus by double gradient dilution method,as well as its physicochemical properties by agar plate diffusion method.The results showed that the minimum inhibitory concentration(MIC)was 2.34μg/mL.Nisin had a good antimicrobial activity at the condition of pH 2 to 6,but gradually weakened at pH 7 to 11.The antimicrobial activity was stable below 100℃,but still had partially activity above 120℃,which indicating its good heat-resistant property.After treated with trypsin,papain and protease K,the antimicrobial activity weakened to some extent,and protease K had the strongest effect.Nisin’s antimicrobial activity showed some synergistic effect with Triton-100 and Tween20,but was significantly inhibited by SDS.