Bio-properties And Applications Of Bacteriocins-producing Strains From Lactic Acid Bacteria In Dairy Products

Four bacteriocin-producing strains were screened from 25 strains of lactic acid bacteria obtained from different sources. They were Lactobacillus acidophilus Ind-I, Pediococcus pentosaceus, Lactobacillus plantanan A and Lactobacillus plantarum B. The effects of carbohydrate and nitrogen on the production of bacteriocin were investigated. The optimum sugar and nitrogen used to produce the largest activity of bacteriocins were sucrose and peptone for L. plantarum A, glucose and peptone for L. plantarum A, lactose and soy peptone forZ,. acidophilus Ind-1, and lactose and peptone for P. pentosaceus, respectively. The initial pH with 6.5 in media allowed the four studied strains to form the highest bacteriocins activity against sensitive organisms. The biological properties of four kinds of bacteriocins showed they were heat stable and did not lost activity when heated at 100癈 for 20 minutes. All the bacteriocins were sensitive to pepsin, proteinase K and trpsin. The three bacteriocins produced by strains L. acidphilus Ind-1, L. plantarum A and B were resistant to the enzyme trpsin, except for the bacteriocin produced by P. pentosaceus. These four bacteriocins showed the highest antibacterial activity under acidulous and neutral conditions. The bacteriocin-producing strains inhibited most of related lactic acid bacteria. The bacteriocins produced by strains L. acidophilus Ind-1 and P. pentosaceu were effective against food spoilage and pathogenic bacteria like Escherichia coli and Staphylococcus aureus. The strains of I. plantarum A and B were effective against many of lactic acid bacteria, but ineffective towards S.aureus, E.coli and Bacillus megaterium. The crude bacteriocins as well as the cells of bacteriocins-producing strains were added to the pasteurized and raw milks to study their effects on the shelf life of dairy products. Addition of bacteriocins produced by L. acidophilus Ind-1 and P. pentosaceu to pasteurized milk led to an extended shelf life of 4 days at 4癈 or 2 days at 22癈. When the cells of the two bacteriocin-producing strains were added to pasteurized milk which was stored at 4癈, it might extended the shelf life of pasteurized milk for at least 3 days. The shelf life of raw milk stored at 4癈 could be extended for 2 days if the bacteriocin-producing cells of L. acidophilus md-1 and P. pentosaceu were added to raw milk. However, addition of the cells of the two bacteriocin-producing strains to pasteurized and/or raw milks were not effective on improving their shelf life when the two kinds of milk were stored at 22癈.