Growth and beta-glucosidase activity of Bifidobacterium

beta-Glucosidase was known to be involved in the mutagenic activation of beta-glucosides. The level of beta-glucosidase in the feces of adults was 2.7 times higher than that of infants. There was no difference in the percentage of beta-glucosidase positive strains among Bifidobacterium isolates between adults and infants, corresponding to 90 and 92%, respectively. However, the strains from adults showed 1.9 times higher enzyme activity than those from infants when grown in Brain Heart Infusion medium. beta-Glucosidase negative strains could not ferment beta-glucosidase substrates, such as cellobiose, salicin, naringin, esculin and arbutin. Presence of beta-glucosidase in Bifidobacterium did not alter the degree of growth in reconstituted skim milk. The beta-glucosidase level was much lower in milk and vegetable medium, although cells grew above 10(8) cfu/ml, than in BHI medium. This study suggests that metabolic activation of the beta-glucosides by Bifidobacterium beta-glucosidase varies significantly depending on types of growth medium.