Abstract:

Laccase was immobilized on N,N′-methylene bis(acrylamide)(BIS) cross-linked poly(methyl acrylic acid) through covalent coupling strategy. The ratio of immobilization was determined and the specific activity of entrapped laccase was measured. Thermal stability, reusability of immobilized laccase and enzymatic parameters for 2,6-dimethoxyphenol(DMP) oxidation catalyzed by immobilized laccase were investigated. Results obtained from experiments indicate that the loading of laccase on this crosslinked copolymer matrix and the specific activity of immobilized laccase can reach up to 26.37 mg/g and 1.202 U/mg respectively. Laccase immobilization on this cross-linked copolymer matrix at 50 ℃ for 2 h can still retain about 83％ of its initial activity and can retain more than 80％ of its initial activity after 10 repeated uses. The apparent velocity constant kcat for DMP oxidation catalyzed by the entrapped enzyme can reach ca.1090 min^-1. The reduction of oxygen at laccaseentrapped BIS cross-linked poly(methyl acrylic acid) modified glassy carbon electrode in phosphate buffer solution(pH=4.4) occurred near +724 mV(vs.SCE).

Key words: laccase, enzyme immobilization, thermal stability, enzymatic kinetics, oxygen reduction reaction