Gelatin blends with alginate: Gel fibers for alpha-galactosidase immobilization and its application in reduction of non-digestible oligosaccharides in soymilk

Abstract

?-Galactosidase from Aspergillus oryzae was physically entrapped in gelatin blended alginate hydrogel fibers hardened with glutaraldehyde. Immobilization yield resulted in 71.75%. The optimum conditions were not affected by immobilization, and the optimum pH and temperature for free and immobilized enzyme were 4.8 and 50 °C, respectively. Immobilized ?-galactosidase was more stable at higher pH and temperature. To improve the immobilization system polyols like glycerol (C3) was used with different amounts of Na-alginate and gelatin. The free ?-galactosidase activity quickly decreased and the half time of the activity decay was about 5 days at 4 °C. The immobilized enzyme remained very active over a long period of time and this enzyme lost about 70% of its original activity over the period of 60 days for storage at 4 °C. Immobilized ?-galactosidase was used in batch, repeated batch and continuous mode to degrade the non-digestible oligosaccharides present in soymilk. The performance of immobilized ?-galactosidase was also tested in a fluidized bed reactor at different flow rates and 93% reduction of NDO in soymilk was obtained at 25 ml h-1 flow rate. The study revealed that alginate-gelatin fiber entrapped ?-galactosidase shows the higher immobilization yield, greater storage stability and better percent hydrolysis of NDO present in soymilk compared to alginate and gelatin entrapped ?-galactosidase. © 2006 Elsevier Ltd. All rights reserved.