以单增李斯特氏菌为指示菌,通过牛津杯双层平板法对从发酵面团样品中分离出的54株乳酸菌进行抑菌试验。在排除有机酸,过氧化氢的干扰后,其中1株乳酸菌的发酵上清液对单增李斯特氏菌仍然表现出明显的抑制作用。其抑菌活性在酸性条件下较强,在加入蛋白酶K和胰蛋白酶以及100℃以上热处理时明显下降甚至消失,说明其代谢产物中含有蛋白质类抑菌物质,是一类细菌素。经Trcine-SDS-PAGE试验分析该细菌素分子质量为25 kDa;经过生理生化试验及16S rDNA序列同源性分析,该菌被鉴定为Lactobacillus curvatus。

54 strains of lactic acid bacteria( LAB) isolated from fermented dough were screened for the antimicrobial activity toward Listeria( L.) monocytogenes by dual-culture agar plate assay. After eliminating the effects of organic acid and hydrogen peroxide,the cell-free supernatant of one strain showed strong antimicrobial activity toward L. monocytogenes. Cell-free culture supernatants of the strain exhibited strong antimicrobial activity under acidic conditions. In addition,the inhibitory activity declined remarkably after digested by protease K and trypsin,and eliminated by heat treatment above 100 ℃. The result showed the inhibitory material which was metabolite of the strain had the features of protein,and could be classified as bacteriocin. The molecular weight of the bacteriocin was approximately 25 kDa by Tricine-SDS-PAGE assay. Based on phenotypic,biochemical tests and 16S rDNA sequence homology analysis,the strain were identified as Lactobacillus curvatus.