Casein digestion by Debaryomyces hansenii isolated from cheese.

To understand the possible proteolytic contribution of yeast during cheese ripening, Debaryomyces hansenii 212 was isolated from commercial blue-veined cheese and incubated in a medium containing casein. Growth and casein degradation were recognized at the cheese-ripening temperature. Proteolytic activity was found in the intracellular fraction, and the enzyme, which was attached to the cell wall, primarily acted on beta-casein. The cytosol contained more than 90% of the total proteolytic activity which was responsible for the degradation of both alpha(s)- and beta-casein. These results suggest that the contribution of yeast to cheese ripening would depend on the susceptibility to cell lysis in addition to its proteolytic activity.