ISOLATION AND PARTIAL PHYSIOLOGICAL CHARACTERIZATION OF COMMERCIAL STRAINS OF BIFIDOBACTERIA

The genus Bifidobacterium has been suggested to be capable of performi ng gastrointestinal modifications, providing nutritional value when ad ded to the diet as a probiotic and having an inducing effect on the im mune system by enhancing cytokine production. As a consequence, the da iry food industry is introducing bifidobacteria to such products as yo gurt, flavored milk, and cottage cheese. The objectives of this projec t were to characterize isolates of bifidobacteria from commercial supp liers, to isolate and characterize bifidobacteria from dairy products, and to establish and compare their physiological characteristics. Phy siological characterization was performed based on phenotypic characte ristics, carbohydrate fermentation patterns, enzyme profiles, fructose -6-phosphate phosphoketolase (F6PPK) assays, and antibiotic sensitivit ies. The results demonstrated that commercial bifidobacteria strains a nd those strains isolated from dairy products were physiologically dif ferent. This demonstrates that some bifidobacteria present in dairy pr oducts may be mischaracterized when identifying their presence based s olely on phenotypic characteristics. The difficulty in growth, rapid a ssessment, and isolation of bifidobacteria from a mixed culture in dai ry products was evaluated in this study. X-alpha-Gal medium was select ed as the most suitable for isolation of bifidobacteria from mixed cul ture products and modified lactobacilli MRS medium for growing pure is olates of bifidobacteria.