Isolation and Evaluation of Probiotic Strains From Dairy Products

Abstract:The present study aimed to isolate, identify and preliminarily characterize strains ofLactobacillus species, Lactococcus species, Bifidobacterium species, Leuconostocspecies,Streptococcus species obtained from dairy products. Samples of raw milk, fermented milk, curd,yogurt, yakult, paneer, cheese and buttermilk were collected from local dairy sources, processedunder aseptic conditions.The isolates were characterized based on colony, morphology, gramstaining and biochemical tests such as catalyzereactions. Samples were serially diluted andcultured on selective media such as MRS Agar and Rogosa SL Agar under anaerobic or microaerophilic conditions at 37 c for 24 – 48 hours. The isolates were found to be gram-positive, non-spore forming and catalyze negative behavior indicating typical characteristics of Lactobacillus, Bifidobacterium, Leuconostoc species of dairy products. These finding confirmthat dairy products are reliable natural sources of probiotic bacteria potential application infunctional food development and human health improvement. The antagonistic properties ofthese isolates against Escherichia coli, Staphylococcus aureus, were examined using agar welldiffusion method. Low pH of fermented dairy products can reduce their survival rate.Temperature and storage time also affect bacterial count and activity