Influence of Bile on ß-Galactosidase Activity of Component Species of Yogurt Starter Cultures

¹ Department of Animal Sciencen, Oklahoma State University, Sntillwater 74078
² Department of Animal Science, Oklahoma State University, Stillwater 74078

The influence of bile on ß-galactosidase activity and the cellular integrity of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius ssp. themphilus were tested. Two strains (OS 1 and OS 2) of L. delbrueckii ssp. bulgaricus and three strains (HC 15, 17, and 18) of S. salivanus ssp. thermophilus were studied. In the presence of .15% oxgall, ß-galactosidase activity of whole cells of both species was significantly increased. However, at a higher concentration (.3% oxgall), the ß-galactosidase activity was significantly less than in the presence of .15% oxgall. The presence of oxgall did not promote the cell lysis of any of the strains of either species. Additionally, the presence of oxgall did not cause the leakage of the enzyme from the cells. Thus, the presence of oxgall increased the cellular permeability to allow more substrate to enter the cells, thereby increasing ß-galactosidase activity, and, at higher concentrations, was inhibitory to ß-galactosidase activity of both species.

Key Words: bile • Lactobacillus delbrueckii ssp. bulgaricus • Streptococcus salivarius ssp. thermophilus • ßbeta;-galactosidase activity

Submitted on February 25, 1994
Accepted on July 12, 1994

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