Isolation and Screening of bacteriocin producing lactic acid bacteria from milk and milk products

One of the most important groups of acid producing bacteria in food industry is the lactic acid bacteria,(LAB). LAB are widespread in nature and predominate in microflora of milk and its products LAB are known to produce bacteriocin and have great potential in food bio preservatives. In the present study a total of 160 strains of LAB were isolated from eight different milk and milk products collected from Dairy Farm, Annamalai University. They were screened for the production of bacteriocin active against Listeria monocytogenes. Among the 160 strains 22 strains were observed as positive bacteriocin producers. The highest percent (25.0%) of bacteriocin producers was recorded in butter followed by yoghurt (20%), curd (18.75%) buffalo milk (16.66%), Goat milk (13.88%) Cheese (11.11%) cow milk (10%) and dairy milk (6.25%). The bacteriocin producers were identified upto generic level as Enterococcus, Lactococcus, Lactobacillus and Streptococcus. There was a striking predominance of the genus Enterococcus (55%) followed by Lactococcus (22%) in the milk and milk products. The spectrum of inhibitory activity of the bacteriocin producers against Gram positive and Gram negative pathogens were tested and observed that, activity is restricted to Gram positive organisms, but Lactobacillus and Streptococcus were active against both Gram positive and Gram negative organisms. The bacteriocins produced by LAB are to be characterized in the further studies