乳链菌肽产生菌的定向筛选及发酵产物的鉴定

DIRECTIONAL SCREENING OF NISIN-PRODUCING LACTOCOCCUS LACTIS AND IDENTIFICATION OF ITS PRODUCT

利用乳链菌肽产生菌中nip^+nis^rsuc^+紧密连锁的原理,在添加乳链菌肽、蔗糖及溴甲酚紫的选择培养基上,从牛奶样品中定向筛选乳链菌肽产生菌。对筛选到的L. lactis1409菌株发酵产物的分析鉴定结果揭示:该产物对多种革兰氏阳性菌有强烈抑制作用,而对革兰氏阴性菌、酵母菌和霉菌无效,在pH值低的条件下对热稳定,对α—胰凝乳蛋白酶敏感,具有生物活性的蛋白质的分子量与乳链菌肽相当,而1409菌株的质粒分布与L. laclisATCC11454和L. lactis 7962不同,说明筛选到的L. laclis 1409菌株确是一株新的乳链菌肽产生菌。

According to which the genetic loci for nisin-producing ability (Nip+), nisin resistance (Nisr) and sucrose-fermenting ability (Suc + ) are linked closely, nisin-producing Lactococcus lactis strains were directionally screened from fresh milk on a selective medium (Ml 7) supplemented with nisin, sucrose and bromocresol purple. Analysis of the fermentation product from L. lactis 1409 revealed that it showed antimicrobial activity against a range of Gram positive bacteria, did not inhibit Gram negative bacteria, yeasts and fungi. Antimicrobial activity was stable at low pH and sensitive to digestion by α-chymotrypsin. The molecular weight of protein band having antimicrobial activity is identical with Nisaplin, while plasmid profiles of L. lactis 1409 are different from L lactis ATCC 11454 and L. lactis 7962. These results indicated that L. lactis 1409 was a new nisin-producing strain.