Lactose hydrolysis from milk/whey in batch and continuous processes by concanavalin A-Celite 545 immobilized Aspergillus oryzae β galactosidase

The present study deals with the immobilization of Aspergillus oryzae β galactosidase on concanavalin A layered Celite 545 as bioaffinity support. The activity yield of crosslinked enzyme was 71%. Michaelis constant, Km was 2.45 mM and 5.58 mM for soluble and crosslinked adsorbed β galactosidase, respectively. Vmax for soluble and crosslinked adsorbed enzyme was 0.52 mM/min and 0.38 mM/min, respectively. Moreover, Kiapp value of crosslinked β galactosidase was 366 × 10−6 M while its soluble counterpart exhibited lower Kiapp value, 181 × 10−6 M at 2% galactose concentration. Soluble and immobilized β galactosidase exhibited same pH and temperature optima at pH 4.5 and 50 °C. The crosslinked adsorbed enzyme retained 90% activity after 1 month of storage at 4 °C and 71% activity after its seventh repeated use. Moreover, crosslinked β galactosidase showed greater resistance to product inhibition mediated by glucose and galactose. Crosslinked Con A-Celite adsorbed β galactosidase showed increased efficiency in hydrolyzing lactose from milk and whey in batch processes at 50 °C as compared to the adsorbed and soluble enzyme. The hydrolysis of lactose in the continuous reactors containing crosslinked β galactosidase was 92% and 81% at flow rate of 20 mL h−1 and 30 mL h−1 after 1 month of operation, respectively.

► The paper summarizes the preparation of a bioaffinity support, concanavalin A layered Celite 545 for the immobilization of Aspergillus oryzae β galactosidase.
► The crosslinked adsorbed β galactosidase exhibited greater stability against various physical and chemical denaturants as compared to the soluble and adsorbed enzyme.
► Moreover, the crosslinked β galactosidase hydrolyzed greater percentage of lactose from milk and whey in batch processes at 50 °C and in continuous reactors at different flow rates.