Cocolin Luca, Foschino Roberto, Comi Giuseppe, Grazia Fortina Maria
Dipartimento di Valorizzazione e Protezione delle Risorse Agroforestali, Università degli Studi di Torino, via Leonardo da Vinci 44, 10095, Grugliasco, Torino, Italy.
Food Microbiol. 2007 Oct-Dec;24(7-8):752-8. doi: 10.1016/j.fm.2007.03.001. Epub 2007 Mar 6.
In this study two strains of Enterococcus faecium, M241 and M249, isolated from goat milk, were studied for their capability to produce antibacterial compounds. It was determined that the bacteriocins produced by both strains were active towards Listeria monocytogenes and Clostridium butyricum, and they did not have any activity with respect to other species of lactic acid bacteria. Enterocins A and B were targeted by polymerase chain reaction (PCR) and sequenced, after cloning, in both strains. The bacteriocins contained in the cell free supernatants were stable when subjected to treatments at high and low temperatures or with lipase, catalase and alpha-amylase. Whereas, the activity was lost when proteinases were used. Lastly, a co-culture experiment with L. monocytogenes in skimmed milk was performed. In the presence of the E. faecium strains, the pathogen showed a delay in the growth of about 6h and it reached a maximum counts of about 10(6) colony forming unit, two orders of magnitude low with respect to the control. This result suggests the possibility to use the strains studied as starter cultures to enhance food safety of dairy products.
在本研究中，对从山羊奶中分离出的两株屎肠球菌M241和M249产生抗菌化合物的能力进行了研究。已确定这两株菌产生的细菌素对单核细胞增生李斯特菌和丁酸梭菌具有活性，而对其他乳酸菌没有任何活性。通过聚合酶链反应（PCR）对两株菌中的肠球菌素A和B进行了靶向扩增，并在克隆后进行了测序。无细胞上清液中所含的细菌素在高温、低温处理或用脂肪酶、过氧化氢酶和α-淀粉酶处理时是稳定的。然而，当使用蛋白酶处理时，其活性丧失。最后，在脱脂牛奶中进行了与单核细胞增生李斯特菌的共培养实验。在屎肠球菌菌株存在的情况下，病原体的生长延迟了约6小时，其最大菌落形成单位数约为10(6)，相对于对照组低两个数量级。这一结果表明，有可能将所研究的菌株用作发酵剂来提高乳制品的食品安全。
