Immobilization of laccase enzyme on magnetically-separable hierarchically-ordered mesocellular mesoporous silica

Abstract

Multicopper oxidases, known as laccase, are a sustainable biocatalyst with efficient ability to degrade a wide range of compounds, environmentally friendly properties and promise major advances in a wide range of industries. However, the use of free laccase in industries often suffers problems, such as instability, low recovery and low reusability of enzyme. Hence, laccase immobilization on a magneticallyseparable hierarchically-ordered mesocellular mesoporous silica (M-HMMS) as the support material was optimized and characterized. In this study, three different immobilization methods used were enzyme adsorption, entrapped-crosslinked enzyme and entrapped-crosslinked enzyme aggregate. The optimum parameters for laccase immobilization were at 5 hr of crosslinking time, 100 mM glutaraldehyde concentration, 1 mg/ml laccase concentration, 60 min time of precipitation with pH 4.5 and temperature of 20 C. This optimal condition contributed to 65.03 ± 4.31 % of laccase activity recovery and enhancement by 2.6 fold. The adsorption of laccase on M-HMMS obeyed the pseudo-second-order kinetic model. The optimized immobilized laccase was able to withstand high temperature (50 ??) and also oxidize 2, 2-azino-bis 3- ethylbenzothiazoline-6- sulfonic acid (ABTS) at a broad range of pH (pH 3.0 to pH 6.0) and temperature (20 to 70c) It also retained 63.72 ± 6.59 % of its initial activity after 8 repeated cycles of ABTS oxidation and 100 % of its activity after 30 days of storage at 4c in pH 4.5 buffer. In conclusion, the optimized immobilized laccase has potential as immobilized biocatalyst for the application of bioremediation and biotransformation of contaminant molecules in water.