Isolation of a bacteriocin-producing Lactococcus lactis subsp lactis and application to control Listeria monocytogenes in Moroccan jben

Aim: Use of a bacteriocin-producing lactococcal strain to control Listeria monocytogenes in jben. Methods and Results: A Lactococcus lactis strain isolated from lben was shown, by the spot technique, to produce a bacteriocin different from nisin. Inhibitory activity of the bacteriocin-producing strain against Listeria monocytogenes was investigated in jben, made from cow's milk fermented with the producer organism and contaminated with 10(4) or 10(7) cfu ml(-1). Listeria counts were monitored during manufacture, and during conservation at room and at refrigeration temperatures. Results showed that the pathogen was reduced by 2.7 logarithmic units after 30 h of jben processing when the initial inoculum of 10(7) cfu ml(-1) was used. For the initial inoculum of 10(4) cfu ml(-1), the bacterium was completely eliminated at 24 h. Furthermore, the use of the bacteriocin-producing starter culture extended the shelf-life of jben by 5 days. Conclusions: In situ production of the lactococcal bacteriocin is an efficient biological means of controlling L. monocytogenes in jben and of allowing shelf-life extension. Significance and Impact of the Study: The proposed technology will essentially benefit minimally processed dairy products and those made with raw milk.