Autolysis of Dairy Propionibacteria in Buffer Systems

Abstract

Autolysis of 21 strains of propionibacteria was studied in buffer systems. Optimal conditions for bacterial autolysis were determined. Maximal autolysis varied between 20 to 80% in potassium phosphate buffer (50 mM; pH 7.0). Autolysis was maximal in the exponential growth phase at 30 to 40°C and at an ionic strength of .3. One pH optimum was observed at pH 7.2. Lysis was stimulated by Na+, K+, and NH4+ and was inhibited by different amounts of Cu2+, Zn2+, Mg2+, and Co2+. Leakage of Pro iminopeptidase followed the degree of autolysis, which verifies an intracellular location of the enzyme. Propionibacteria seemed to contain a glycosidase and an N-acetylmuramyl-L-alanine amidase or an endopeptidase. © 1995, American Dairy Science Association. All rights reserved.