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

α-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 α-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 α-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 α-galactosidase was used in batch, repeated batch and continuous mode to degrade the non-digestible oligosaccharides present in soymilk. The performance of immobilized α-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 α-galactosidase shows the higher immobilization yield, greater storage stability and better percent hydrolysis of NDO present in soymilk compared to alginate and gelatin entrapped α-galactosidase.