Study of β-galactosidase activity in Lactobacilli separated from milk and cheese by biochemical and PCR methods

In some people the inadequate amount of Beta-galactosidase enzyme, in layer of villous epithelium of the small intestine, causes the disorder of lactose intolerance. This examination was done to observe the existence of Beta-galactosidase enzyme that is produced by separated Lactobacillus from samples of dairy products (milk and cheese). Pasteurized and local samples of milk and cheese were perchased from Lorestan,Ilam and Hamedan provinces. By keeping the samples in MRS media and according to some phenotypic features, Lactobacillus were recognized. Through X-gal and ONPG methods the ability of Beta-galactosidase production was examined.By PCR method the existence of Beta- galactosidase gene was studied. Among studied samples 131 Lactobacillus(13 strains) were separated,which in media containing X-gal green colonies were acquired(but in different occasions).Green colonies demonstrated the existence of Beta-galactosidase enzyme in the media. In ONPG test, all Lactobacillus indicated the Beta-galactosidase activiy that in 25 strains the amount of enzyme was more than the others, (also the greatest amount of enzyme in a strain of Lactobacillus delberoki separated from Kermanshah local cheese was measured by 2010 miller unit /ml). In a standard strain of Lactobacillus Plantarum(RITCC 1273) and 29 strains of separated Lactobacillus Plantarum the 399bp band of Beta-galactosidase gene was examined and confirmed through PCR method. In dairy products, using Lactobacilli which contain Beta-galactosidase enzyme,we can help the people who lack lactose tolerance. Meanwhile those Lactobacillus that creat more Beta-galactosidase are more suitable to use.