Abstract
A strain of Aspergillus niger selected by an extensive screening test was found to secrete a large amount of lipase when grown on the bran-Koji medium. The enzyme was purified from the water extract of bran-Koji by fractionations with ammonium sulfate and acetone, followed by acid treatment, acrinol precipitation and ion exchange chromatography. It was finally obtained in a crystalline form from a solution in acetone.
Electrophoretic analysis showed that the crystalline enzyme was a single protein. Its activity did not decrease on exhaustive dialysis against water, suggesting the absence of a dialyzable co-factor. The crystalline enzyme hydrolyzes olive oil almost completely, whereas it does not attack methyl butyrate at all. The action of the enzyme upon olive oil has the optimum pH at about 5.6 and the optimum temperature at 25°. The enzyme was stable at the pH range between 2.2 and 6.8, and at pH 5.6 it could resist temperatures up to 50° for 15min.
