| In order to degrade and transform the cholesterol in food stuff,the strain Penicillium sp.TS406,which secret Cholesterol oxidase in fermented culturing,was mutated by complex mutagenesis,cholesterol oxidase was isolated and purified,the property and the application to egg yolk of the enzyme was studied.Through DES(3%) Combining UV mutate,higher productivity strain was screened out,then was treated by NTG(1.2mg/ml) combine UV.,A mutant,named penicillium N81 showed highest production of cholesterol oxidase,was obtained,the enzyme activity of the strain was increased from 546U/L to 1267U/L.Genetic stability of the mutated stain NS1 was testified through SPSS analysis,the results showed the strain N81 is stable in producing cholesterol oxidase.The cholesterol oxidase was isolated and purified from the broth of strain TS406 by Sephadex G-75 gel filtration and DEAE-Sephadex A-50.The activity of the enzyme was 16.068U/mg.SDS-PAGE showed that cholesterol oxidase consist of a single peptide chain.The activity of the Cholesterol oxidase was detected at different reaction conditions,the results showed that the optimum temperature of the enzyme reaction is 45℃,and pH 7.5, Cholesterol oxidase is stable at the temperature lower than 40℃,the Km=5.0×10-4.The egg yolk was treated with cholesterol oxidase,the results showed that cholesterol is obvious reducing by 33.8%after 24 hours.
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