 Propagation of fermented product using bacterial culture Introduction Yogurt is produced by bacterial fermentation of milk The organisms that are used to make yogurt are known as yogurt culture Mainly consists of Lactobacillus bulgaricus and streptococcus thermophilus The lacticated bacteria are also used for this process Bacteria mostly ferment lactose into lactic acid Which act on milk protein that gives yogurt characteristic texture and tart flavor Mainly it is produced from different milk sources For example milk from cow, goat, sheep, skim milk Fat milk, low fat milk and milk from plant origin such as soy milk Lactobacillus are commonly used in food industries And these bacteria have ability to ferment the lactose into lactic acid Which is the basic product after inoculation into the milk For the preparation of fermented product which is yogurt Falling procedure is used Regents and materials required Milk sample, heating loop, burner, test tube containing sterile distilled water For serial dilution collect milk sample from cow And pasteurize at 85 degree centigrade for 30 minutes After pasteurization cool milk sample to 37 degree centigrade This is lactobacillus stain isolated and identified Inoculating loop to red hot for 1 to 2 minutes Now take single colony of lactobacillus milk sample With the help of inoculating loop to inoculation to red hot again Properly and placed in incubator at 42 degree centigrade for 4 to 6 hours After incubation for 4 to 6 hours Yogurt is prepared by the fermentation of lactose into lactic acid Which is commonly produced with the help of lactobacillus species Most commonly lactobacillus vulgaricus and streptococcus thermophilus