Biochemical activities of Bacillus species isolated from flat sour evaporated milk.

Forty strains of bacilli were isolated from flat sour evaporated milk and were characterized as Bacillus stearothermophilus (5 strains), Bacillus licheniformis (10 strains), Bacillus coagulans (15 strains), Bacillus macerans (5 strains), and Bacillus subtilis (5 strains). The hydrolases of these strains were examined with the API ZYM system, and the ability of these strains to produce acid in milk incubated at different temperatures was also examined. Esterase, esterase lipase, lipase, valine aminopeptidase, phosphoamidase, beta-glucuronidase, and beta-glucosidase were the activities found in all strains tested; they were strain-dependent and ranged between 1 and 5 by the API ZYM test. The same strains produced various concentrations of acid in milk. These organisms may be responsible for the flat sour spoilage in evaporated milk.