Hydrolysis of galacto-oligosaccharides in soymilk by immobilized α-galactosidase from Chaetomium madarasense AUMC 9376

摘要

a-galactosidase 3.2.1.22 (a-Gal) enzyme was produced from Chaetomium madarasense AUMC 9376 under solid state fermentation using banana peels as substrate. Optimal a—Gal production was obtained at initial pH 5 and, 40°C then the enzyme was completely purified resulting in 25.32 folds purification (1561.67 U/mg). The enzyme was immobilized in technical grade sodium alginate and gelatin. The characteristics of the free and immobilized enzyme were also investigated. The optimum temperature for both enzymes was 50°C and 60°C, respectively, while, the optimum pH for both was 5. Besides, the pH stability and thermal stability of the free and immobilized enzyme were also studied. Immobilized a—Gal was more stable at high pH and temperatures than the soluble one. The results showed that the catalytic properties of the immobilized enzyme were improved. Moreover, HPLC chromatograms revealed that the immobilized enzyme has the ability to reduce raffinose and stachyose oligosaccharides in soymilk by 69.2 and 64.3%, respectively.