Abstract
Background and Aim. The increasing demand for inexpensive milk coagulants stimulates the search for new sources of milk-forming enzymes among proteolytic microorganisms. The aim of this work was to isolate a strain with proteolytic activity. Materials and Methods. In the present study, a proteolytic strain of Bacillus paralicheniformis T7 was isolated and identified. By culturing B. paralicheniformis T7 for three days on feather medium, an enzymatic extract with proteolytic activity of 715.7 ± 40.2U/mL was obtained. In addition to proteolytic activity, the B. paralicheniformis T7 strain also exhibited amylase (176.1 ± 16.3), esterase (24.3 ± 0.4), lipase (17.5 ± 0.8), and phosphatase (11.9 ± 0.6) activities. Results. Zymographic analysis using casein showed that the extract contained caseinolytic proteases. Proteases from B. paralicheniformis T7 completely hydrolyzed of 1 mg casein in 90 s. Six proteases, as well as esterase, amylase, phosphatase were identified in the extract by HPLC-Q/TOF analysis. In addition to caseinolytic activity, B. paralicheniformis extract has milk-clotting activity, which was 12 and 23 U/mL for cow's and ewes' milk, respectively. Cheese was produced from fresh cow's milk using the enzymatic extract, with a yield of 17%. Conclusion. The use of the B. paralicheniformis T7 strain as a new source of proteolytic enzymes, and its proteases as milk-clotting enzymes in the cheese-making industry, appears promising.