Degradation of phenolic inhibitors by laccase immobilized on tannic acid/polyethylenimine modified magnetic nanoparticles

Abstract

Magnetic Fe3O4 nanoparticles were successfully functionalized with the low-cost mussel-inspired tannic acid (TA)/polyethylenimine (PEI) under mild conditions and then activated with glutaraldehyde (GA) to covalently immobilize laccase for degradation of four model phenolic inhibitors commonly found in lignocellulosic hydrolysate. The immobilized laccase showed the highest relative enzyme activity with the laccase loading of 39.9 mg/g and the enzyme activity recovery of 53.1%. Compared with free laccase, immobilized laccase possessed better relative enzyme activity at acidic pH and wide temperature range, as well as exhibited excellent storage stability and satisfactory reusability. Moreover, it was found that the phenolic degradation products by immobilized laccase did not exhibit obvious inhibition on subsequent enzymatic cellulose hydrolysis. Thus, the low-cost TA/PEI coating for modification of magnetic nanoparticles will provide a promising support for laccase immobilization and the immobilized laccase has great potential in removal of phenolic inhibitors present in lignocellulosic hydrolysate.

Keywords

• Magnetic nanoparticles
• Enzyme immobilization
• Laccase
• Catechol/polyamine
• Tannic acid