Assigning the Probiotic Potential of Lactic Acid Bacteria Recovered from Popular Egyptian Fermented Artisanal Dairy Products

Abstract

Various artisanal dairy products such as kariesh cheese, Laban Rayeb (a type of fermented fluid milk), zabady (a type of artisanal yoghurt), Butter milk and soured cream (a type of cream separted from skim milk after overnight natural fermentation of milk in earthenware pots) are poular for human consumption in Egypt. However, they are manufactured from raw milk depending on natural fermentation by wild microflora without guaranteed heat treatment processing or addition of permissible additives. Thus, the current study included the microbiological investigations on 50 samples of each of afore-mentioned products (total of 250 samples) primarily to isolate and discriminate different lactic acid bacteria (LAB) flora and secondly to search for some LAB to be further considered as a probiotic culture. Accordingly, several characteristics were investigated including, their ability to resist and survive gastrointestinal tract conditions represented in gastric acidity (pH 3) and duodenal bile acids, and at the same time, ability to produce antimicrobial substances such as organic acids (lactic acid), hydrogen peroxide and diacetyl. At the same time, the isolates were tested for having safety or non-pathogenicity, which principally includes non-harboring of antibiotic resistance (AR) features or blood haemolysis activity. Three important technological properties including the salt tolerance, β-galactosidase production and milk acidification ability were tested for selected isolates as important features needed for optimum fermentation by LAB as starter or non-starter cultures that can be incorporated in dairy processing. Finally, the LAB strains were tested as inhibitors for bacteria of food-safety concern such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. Our results showed that the examined fermented artisanal dairy products proved to harbor a wide variety of LAB microflora. After screening the probiotic, technological and safety related properties of 40 selected LAB isolates from examined products, 7 strains were proven to meet all required criteria, thus could be tested in future studies as promising strains to be incorporated in manufacture of various dairy products as starter and non-starter cultures.