Lactose-Free Milk Preparation by Immobilized Lactase in Glass Microsphere Bed Reactor

Abstract

The high prevalence of lactose intolerance was observed in Asian population. Lactose-free milk is a beneficial product to ameliorate this disorder. A lactase immobilized catalytic system for lactose-free milk preparation was established in the present study. The results show that lactase was covalently immobilized on the glass microspheres exhibited a highly efficient catalytic manner (the immobilization yield is about 83.2%) over other three solid carriers (PAN beads, cellulose beads, and nylon pellets). Optimal conditions were determined to be at room temperature and pH 6.0 using O-nitrophenyl-D-galactopyranoside as an indicator. Scanning electron microscopy and electron spectroscopy for chemical analysis provided direct evidence that lactase was successfully immobilized on the glass microspheres. Operational reusability was confirmed for more than 10 batch reactions and the stability was capable of sustaining catalytic activity for 62 days (the relative activity is still around 60%). Flow rate of 60 mL/h in the packed lactase immobilized on glass microspheres reactor is the optimal condition for lactose-free milk preparation. Lactose within milk can be completely hydrolyzed in 33.3 min. These results provided a good indication for the procedure for lactose-free milk preparation in dairy industry.