Carbodiimide coupling of β-galactosidase from Aspergillus oryzae to alginate

β-Galactosidase from Aspergillus oryzae was bound to water-soluble alginate using the carbodiimide coupling procedure. N-Hydroxysuccinimide (NHS) was found superior to other acidic compounds. A molar ratio of 0.2/I of NHS/EDC was found optimal. The coupling process was completed within 12 h. The bound enzyme was subsequently entrapped in calcium alginate beads. The mass balance of active bound enzyme (measured in solution after redissolving the beads), active unbound enzyme (measured after carefully washing the beads), and nonrecoverable enzyme activity was determined. Using a charge of 22 × 10 3 units g −1 carrier, 12 × 10 3 units g −1 carrier were active bound with a sequential addition of chemicals and enzyme, and the nonrecoverable activity was only 5 × 10 3 units g −1 carrier. Thus, a total of 76% of the charged enzyme could be recovered. A maximum load of 22 × 10 3 units active bound enzyme g −1 carrier could be achieved.