High Molecular Weight alpha-Galactosidase from the Novel Strain Aspergillus sp. D-23 and Its Hydrolysis Performance

Aspergillus sp. D-23 was obtained by ultraviolet-diethyl sulfate (UV-DES) compound mutagenesis from Aspergillus sp. C18 that the alpha-galactosidase was purified from. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and non-denaturing polyacrylamide gel electrophoresis (Native-PAGE), the purified enzyme demonstrated apparent homogeneity. The monomeric alpha-galactosidase's native molecular weight was 125 kDa. The optimal temperature of alpha-galactosidase was 65 degrees C, and 75% of the initial enzyme activity could be maintained between 45 and 55 degrees C. Its optimal pH was 5.0 with good pH stability. After incubating for 2 h at pH 3.0-8.0, it could retain more than 80% of its original activity. Different concentrations of metal ions had different effects on the alpha-galactosidase activity. High concentrations of Cu2+ could strongly inhibit enzyme activity and low concentrations of Fe2+ could promote enzyme activity. Additionally, as shown by thin layer chromatography and high-performance liquid chromatography, the enzyme also had good hydrolysis ability, which could efficiently hydrolyze melibiose and raffinose by more than 95%. Therefore, these excellent characteristics could make alpha-galactosidase a good candidate for the food and feed industries.