Calcium alginate entrapped preparations of Aspergillus oryzae β galactosidase: Its stability and applications in the hydrolysis of lactose

Insoluble concanavalin A–β galactosidase complex was obtained by using jack bean extract and this complex was crosslinked with glutaraldehyde, in order to maintain the integrity of complex in the presence of its substrate or products. Concanavalin A–β galactosidase complex retained 92% of the initial enzyme activity whereas crosslinked complex showed 88% activity. Entrapment of concanavalin A–β galactosidase complex into calcium alginate beads provided suitability to use this preparation in reactors. Temperature- and pH-optima of the various immobilized β galactosidase preparations were the same as its soluble counterpart. Entrapped crosslinked concanavalin A–β galactosidase complex retained more than 50% activity after 1 h exposure with 4.0 M urea at room temperature. Moreover, entrapped crosslinked concanavalin A–β galactosidase complex retained 81 and 62% of the original enzymatic activity in the presence of 5% calcium chloride and 5% galactose, respectively. Entrapped crosslinked concanavalin A–β galactosidase complex preparation was more superior in the continuous hydrolysis of lactose in a batch process as compared to the other entrapped preparations. This entrapped crosslinked concanavalin A–β galactosidase complex retained 95% activity after seventh repeated use and 93% of its original activity even after 2 months storage at 4 °C.