Hydrolysis of Galacto-oligosaccharides in Soymilk by κ-carrageenan-entrapped α-galactosidase from Aspergillus Oryzae

Abstract

α-Galactosidase was immobilized in κ-carrageenan. The optimum pH of the soluble enzyme and immobilized enzyme was 4.8. The optimum temperature of the soluble enzyme was 50 °C and that of the immobilized enzyme was increased to 53 °C. The immobilized enzyme was used in batch, repeated batch, and in the continuous mode to degrade the raffinose family sugars present in soymilk. Two hours incubation with free and immobilized α-galactosidase resulted in 88 and 75% reduction in raffinose family oligosaccharides in soymilk respectively. In the repeated batch, 61% reduction was obtained in the fourth cycle. A fluidized bed reactor was designed to treat soymilk continuously. The performance of immobilized α-galactosidase was also tested in a fluidized bed reactor at different flow rates and 92% reduction of raffinose family oligosaccharides in soymilk was obtained at 25 ml h−1 flow rate. The study revealed that immobilized α-galactosidase in continuous mode is efficient in reducing the oligosaccharides present in the soymilk.