Optimization of operational conditions for biodegradation of chlorophenols by laccase-polyacrilonitrile beads system

Abstract The oxidative biodegradation of 2- and 4-chlorophenol (CPs) catalyzed by immobilized laccase from Trametes versicolor was conducted in a bed reactor. The effects of reaction conditions (reaction time, dosage of immobilized enzyme, flow rate, pH value and temperature, initial concentration) on CPs removal efficiency ( RE ) were investigated. By using in the immobilization solution an enzyme dosage of 2.5  mg free enz g carrier − 1 , the maximum ratio of laccase to PAN-beads is resulted 0.25  mg imm enz g carrier − 1 . RE values greater than 70% were obtained when 40 mL of 1 mM substrate solution were circulated for 90 min at 75 mL min −1 in the bed reactor filled with 12 g of laccase-PAN beads. The optimal pH for CPs biodegradation was 5 and it was not related to substituent position on aromatic ring. Experiments with immobilized laccase demonstrated good removal at high initial substrate concentrations and high thermal stability. The affinity of 2-CP was higher than that of 4-CP. Finally, the 2-CP was also biodegraded as tertiary mixtures with 2,3,4,5-tetrachlorophenol (TCP) and pentachlorophenol (PCP). The presence of TCP and PCP decreased the removal efficiency of 2-CP. The order of the relative degrading capacity becomes TCP > PCP > 2-CP.