摘要：For the production of yogurt and related products, the local and the commercial yogurt manufacturers of Pakistan are still, by and large using an undefined, unclassified mixture of lactic acid bacteria together with a large number of contaminated strains. Phages isolated in our part of world show different characteristics in terms of phage morphology, lytic patterns and burst size etc, compared to phages isolated elsewhere in the world cause serious problems to fermentation process and ultimate economic losses to dairy industry. In order to develop indigenous resistant starter cultures phages were isolated from samples of Dahi whey isolated phages were characterized on the basis of host range, latent period and burst size. Five virulent phages KT-1, KT-2, KT-3, KT-4 and KT-5 were isolated from twelve samples of whey using Lactococcus lactis strains as host. These phages caused lysis and ultimately retarded acid production of host strains. Three phages i.e. KT-1, KT-2 and KT-3 have shown multiple host specificity. Phages KT-1 and KT-2 have same latent period of 15 minutes but exhibited a slightly different rise period that is 20 minutes and 25 minutes respectively, the burst size of 90 and 65 phages per cell were detected for KT-1 and KT-2 respectively. KT-4 showed burst size of 80 phages per infected cell, whereas KT-5 showed burst size of 90 phages per cell. The results reveal that bacteriophages from this region are different from phages isolated in other parts of world.
