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Appl Environ Microbiol. 1972 January; 23(1): 21-25
Copyright © 1971 American Society for Microbiology. All Rights Reserved.

Stimulation of Lactic Streptococci in Milk by ß-Galactosidase1

S. E. Gilliland, M. L. Speck and J. R. Woodard Jr.2

a Department of Food Science, North Carolina State University, Raleigh, North Carolina 27607

ABSTRACT

Acid production in milk by lactic streptococci was stimulated by added ß-galactosidase. Both glucose and galactose accumulated rapidly in the presence of this enzyme. Glucose accumulation ceased as the culture entered the most rapid period of acid production, whereas galactose accumulation continued. In cultures without added ß-galactosidase, a low concentration of galactose accumulated in the milk, whereas glucose was not detected after 2 hr of incubation. Cultures grew and produced acid faster in broth containing glucose rather than galactose or lactose. These observations suggest that the lactic streptococci do not metabolize the lactose in milk efficiently enough to permit optimum acid production and that a phenomenon such as catabolite repression functions to allow for a preferential use of glucose over either galactose or lactose. In addition to providing the culture with a more readily available energy source, it is possible that the culture produced more acidic metabolites as a result of preferentially utilizing the glucose released by the action of the ß-galactosidase.

FOOTNOTES

2 Present address: Becton Dickinson Research Center, Raleigh, N.C.

1 Paper no. 3542 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, N.C.

Appl Environ Microbiol. 1972 January; 23(1): 21-25
Copyright © 1971 American Society for Microbiology. All Rights Reserved.





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