Hydrolysis of galacto-oligosaccharides in soymilk by kappa-carrageenan-entrapped alpha-galactosidase from Aspergillus Oryzae

Abstract

alpha-Galactosidase was immobilized in kappa-carrageenan. The optimum pH of the soluble enzyme and immobilized enzyme was 4.8. The optimum temperature of the soluble enzyme was 50 degrees C and that of the immobilized enzyme was increased to 53 degrees 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 alpha-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 alpha-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 alpha-galactosidase in continuous mode is efficient in reducing the oligosaccharides present in the soymilk.