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Journal of Dairy Science Vol. 60 No. 11 1677-1682
© 1977 by American Dairy Science Association ®
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Species Differences and Effect of Incubation Time on Lactic Streptococcal Intracellular Proteolytic Enzyme Activity1

R. H. Schmidt, H. A. Morris and L. L. Mckay

Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108

ABSTRACT

Ruptured cells of Streptococcus lactis C2, S. cremoris ML 1 and a lactose-negative proteinase-negative (Lac-Prt) mutant of S. lactis C2 (LMO220) were fractionated into the soluble, particulate, and ribosome fractions by differential centrifugation. S. lactis C2 possessed higher activity of intracellular proteinase, alanyl-glycinase, particulate associated dipeptidase and ribosome associated dipeptidase than did S. cremoris ML1. LMO220 was lower in intracellular proteinase and dipeptidase activity and lower in ribosome associated dipeptidase activity than was the parent strain C2. Particulate associated dipeptidase activity was substantially higher in the mutant cells. Extending incubation times from 5 to 24 and 32 h reduced intracellular proteinase and ribosome associated dipeptidase activity in S. lactis C2 and S. cremoris ML1. Soluble alanylglycinase activity and particulate associated dipeptidase activity of ML1 were reduced drastically after 24-h incubation.

FOOTNOTES

1 The data in this paper are from a thesis presented by R. H. Schmidt in partial fulfillment of the requirements for the degree of Doctor of Philosophy, University of Minnesota. Scientific Journal Series Paper no. 9828, Minnesota Agricultural Experiment Station, St. Paul 55108, Presented, in part, at the 69th Annual Meeting of the American Dairy Science Association, University of Guelph, Guelph, Ontario, Canada, June 23-26, 1974.

2 Department of Food Science, University of Florida, Gainesville 32611






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