Oxidative degradation of polyaromatic hydrocarbons catalyzed by blue laccase from Pleurotus ostreatus Dl in the presence of synthetic mediators

摘要

The laccase produced by the white-rot fungus Pleurotus ostreatus Dl (BLPO) under submerged cultivation was purified to homogeneity.Its catalytic activity towards several phenolic compounds,including ABTS (2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt),syringaldazine (4-hydroxy-3,5-dimethoxybenzaldehyde azine),2,6-dimethoxyphenol and catechol was investigated.pH-optima and kinetic constants (K_m and V_(max)) of these reactions were determined.The enzyme was able to degrade the following polyaromatic hydrocarbons (PAHs):anthracene (91%),phenanthrene (72%),fluorene (53.5%),pyrene (65.5%),fluoranthene (69.7%),and perylene (73%) only in the presence of a synthetic mediator.The degradation of phenanthrene in the presence of detergents varied from 49% to 72%,whereas in the absence of any detergent it reached 10%.Investigating the effect of various mediators on PAHs degradation by the BLPO showed that ABTS was a better mediator of anthracene oxidation and HBT (1-hydroxybenzotriazole) was a better mediator of fluorene oxidation.Pyrene and anthracene were degraded more rapidly in a mixture than separately.The effect of different solvents on the activity of the BLPO towards anthracene and fluorene was investigated also.Finally,it was found that in a solution of 30% (v/v) acetonitrile,BLPO could degrade about 56% of the 600 mu M initially added anthracene with the formation of anthraquinone.