Qom University of Medical Sciences Journal

Background and objective Lactose intolerance is a discomfort state that occurs in some people after ingestion of milk and it is due to insufficient amount of beta galactosidase in the human gut to digest lactose. The aim of this study was to observe the presence of beta galactosidase enzyme produced by isolated lactobacilli from milk and cheese. Methods In this deh1ive study milk and cheese samples with different brand were bought from different shops. Lactobacilli were identified by plating samples on MRS medium Gram staining and standard biochemical methods. β-galactosidase production by bacteria was assessed by X-Gal and ONPG methods. β-galactosidase was also detected by SDS-PAGE. Results Fourteen genus of lactobacillus were isolated From 50 samples. All of the bacteria produced green color colonies on X-Gal plates (but in different times) that indicated the presence of enzyme in the bacteria. All isolated lactobacilli were shown β-galactosidase activity in ONPG test. The highest enzymatic activity was seen in one strain of Lactobacillus Delbrueckii (1966 Miller unit /ml). In some bacteria (37%) a strong β-galactosidase band(116-kDa) was seen by SDS-PAGE. Conclusion Addition of beta galactosidase containing lactobacilli as a probiotic agent to milk cheese and other dairy products could ameliorate lactose intolerance. Meanwhile X-gal and ONPG methods which are simple rapid and cheap can be used instead of SDS-PAGE.