Autolysis of Dairy Propionibacteria in Buffer Systems

¹ Department of Food Science, Agricultural University of Norway, PO Box 5036, Ås-NLH, Norway

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.

Key Words: autolysis • propionibacteria • buffer studies

Submitted on January 30, 1995
Accepted on May 12, 1995