Molecular Identification of Lactobacilli in Milk

A total number of 35 raw milk samples were used in this study to isolate and identify the lactobacillus and to find out the incidence of lactobacillus in milk. From all the lactobacillus isolates DNA was extracted using a commercial Kit and quantified. The concentration of DNA varied from 55-200 ng/ìl and purity ranged from 1.5- 1.9. The size of the DNA was more than 20 Kb. PCR test showed positive reaction for all the 30 isolates of lactobacillus with genus specific primer and amplicon size was 0.4Kb. PCR from raw milk DNA without added lactobacilli showed negative reaction. Twelve suspected isolates of L.acidophilus tested for species specific PCR, showed positive reaction and size of amplicon was 550bp . In order to validate PCR, raw milk was intentionally 7 5 added with different dilutions of lactobacilli (10 , 10 , 103, 101) and PCR was carried out. Up to 103 cfu/ml of lactobacilli in raw milk showed positive reaction in PCR. This study concluded that 103 cfu/ml is required to identify the lactobacillus from raw milk by PCR.