Clarification of Sugarcane Juice Catalyzed by Magnetic Immobilized Laccase Intensified by Alternating Magnetic Field

In this study, Cu2+-chelated magnetic silicon dioxide nanoparticles were synthesized as carriers for laccase immobilization. The prepared magnetic immobilized laccase was applied in the clarification of sugarcane juice. The optimal conditions for the clarification of sugarcane juice with magnetic immobilized laccase in a shake flask were determined to be as follows: a temperature of 35 degrees C, pH of 5.5, rotation speed of 150 r/min, and immobilized laccase dosage of 1.0 mg/mL. The sucrose in the sugarcane juice inhibited both free and immobilized laccase. The inhibitory effect was characterized as mixed inhibition, wherein competitive inhibition played a dominant role. An alternating magnetic field was introduced into the catalysis process using magnetic immobilized laccase, and the catechin degradation rate was improved to 77.2% under a magnetic field intensity of 80 Gs and magnetic field frequency of 400 Hz. Under the optimal alternating magnetic field conditions, the treatment time of sugarcane juice was reduced to 20 min when catalyzed by the magnetic immobilized laccase, wherein a decolorization rate of 54.4%, reduction in turbidity of 89.7%, and total phenol degradation rate of 43.4% were achieved. Compared with the shaking condition, the assistance of alternating magnetic fields can shorten the clarifying time, increase the clarifying effect, and enhance the catalyst reusability. These results reveal useful information about the enzymatic treatment of high-sugar juice and provide a potential strategy for juice clarification with magnetic immobilized enzymes.