Isolation and identification of microorganisms and antibacterial activity of Laban Zeer, an Egyptian traditional fermented milk product

Abstract

Laban Zeer is a traditional Egyptian fermented milk product. The microorganisms of Laban Zeer were isolated and identified to species level, as well as the antibacterial activity of Laban Zeer was also studied against pathogenic bacteria. Total viable microorganisms, including, lactic acid bacteria (LAB), aerobic mesophilic bacterial, Enterococus and Enterobacteriaceae were enumerated. A total forty eight LAB and twenty eight yeast isolates were isolated from four Laban Zeer samples and identified by API 50 CHL and API 20C AUX identification system, respectively. The avenger of LAB counts were 7.4 cfu/g, while yeast and Enterococus counts were 4.67 and 4.39 cfu/g, respectively. It is noted that the count of bacteria belonging to the family of Enterobacteriaceae was not detected in all tested samples. The LAB species were identified as Leuconostoc mesenteroides subsp. cremoris, Lb. rhamnosus, Lb. plantarum, Lb. paracasei subsp paracasei, Lb. delbercii subsp bulgaricus, Lb. curvatus subsp curvatus and Lb acidophilus. The isolated yeasts were identified as Sccharomyces cervisiae , Candida kefyr , Candida utilis and Rhodotorula mucilaginosa. The most frequently isolated species was found to be Leuconostoc mesenteroides subsp. cremoris (37.5%) , Lb. rhamnosus (20.8%), Sccharomyces cervisiae (41.9%) and Candida kefyr (29.0%). The antimicrobial activities of Laban Zeer were evaluated in vitro using an agar well diffusion method and in situ method. The major supernatants of Laban Zeer samples inhibited the growth of pathogenic bacteria, belonging to Escherichia , Pseudomonas , Salmonella , Listeria and Staphylococcus genera in various degrees. The in situ method was performed by the inoculation of Staph. aureus and E. coli in Laban Zeer samples separately at an initial level around of 6 log cfu/ml. The count of Staph. aureus and E. coli were not detected after 12 and 3 days of refrigerated storage period, respectively in samples number 2 and 3. Laban Zeer is not suitable environment for growth and activity of such pathogen and would eliminate the pathogen early enough before the products were made ready for consumption. The microorganisms isolated from Laban Zeer can be used widely in the food fermentation industry as starter culture and bio-preservatives due to their broad inhibition spectrum.