RESUMO
Two gram-positive microorganisms, a spore-forming rod and a coccus, were isolated from a can of evaporated milk which had coagulated after storage at 37°C for 3 months. The two strains were identified as Bacillus subtilis and Enterococcus faecium , respectively. Individually, neither strain produced acid in sterile skim milk; however, when cultured together, the pH dropped rapidly and the milk coagulated. Similar results were obtained with E. faecium and a proteolytic Pseudomonas sp. Acid production by E. faecium in sterile skim milk was closely related to proteolysis produced by addition of partially purified B. subtilis proteinase. Acid production was also stimulated by addition of enzymatic digests of casein. It was concluded that spoilage in canned evaporated milk had resulted from production of acid by E. faecium when supplied with small molecular weight nitrogenous compounds derived from milk proteins by the action of B. subtilis proteinase.
