Activity of Bacillus cereus Proteinases in Milk

Abstract

The selective activity of the proteinase enzyme system of a strain of Bacillus cereus was determined in sterile nonheated and pasteurized skimmilks. They were inoculated with B. cereus spores, incubated at 35 C for 12 hours, and changes in the protein system were followed by polyacrylamide gel disc electrophoresis. For the proteins soluble in acid whey, two major changes were noted in the electrophoretic patterns: The proteose-peptone fraction disappeared completely within 12 hours and a new fraction appeared with a mobility similar to that of the dye marker. The caseins were degraded, being more pronounced for β- than for αs-casein and more rapid in pasteurized than in raw unheated skimmilk.