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KMID : 0545119920020010014
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Journal of Microbiology and Biotechnology
1992 Volume.2 No. 1 p.14 ~ p.20
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Purification and Characterization of Soymilk-clotting Enzyme Produced by Penicillium sp.
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Koo, Sung Keun
Lee, Sang Ok/Lee, Tae Ho
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Abstract
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Some microorganisms isolated from soil, including some bacteria and fungi, were found to secrete an extracellular soymilk-clotting enzyme. Among them, an isolated fungus showed the highest soymilk-clotting activity and the strain was assigned to genus Penicillium based on its cultural and morphological characteristics, and designated as Penicillium sp. L-151V, Soymilkclotting enzymes A and B produced by Penicillium sp. L-151K were purified by ammonium sulfate precipitation and chromatographies on Sephadex G-25, CM-Sephadex, Sephadex G-100 and phenyl-Toyopearl gel. The two purified enzymes A and B were found to be homogeneous by polyacrylamide gel electrophoresis at pH 9.5. The molecular weights of enzyme A and B were 24,000 and 40,000, respectively, by gel filtration on Sephadex G-100. Enzymes A and B coagulated soymilk optimally at 60℃ and were stable up to 50℃. Both enzymes were most active at pH 5.8 for soymilk coagulation, and were stable with approximately 80% of original activity from pH 3.0 to 5.0. Each enzyme was an acidic protease with an optimum pH of 3.0 for casein digestion. The soymilk-clotting efficiency of these enzymes was improved with CaCl_2 or MgCl_2 when making soymilk-curd.
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