Degradation of pentachlorophenol by selected species of white rot fungi.

Abstract

The focus of this research was to examine the potential for using white rot fungi to degrade pentachlorophenol (PCP) in water. Experiments were designed to determine the optimum growth conditions for 4 species of fungi, quantify toxicity of PCP to 18 species, and examine PCP degradation by both extracellular enzymes and whole cultures of 4 species. Optimum growth temperatures ranged from 25°C for G. oregonense to 40°C from P. chrysosporium with I. dryophilus and T. versicolor at approximately 30°C. Optimum growth pH were 4.5 for Phanerochaete chrysosporium and 6.0 for the other 3 species. Eighteen species tested for PCP sensitivity were inhibited by 10 mg-PCP/L when grown on agar plates. Within 2 weeks, 17 of the 18 species grew in the inhibition zones. In liquid phase toxicity experiments, all 18 species were killed by 5 mg-PCP /L. Further liquid testing showed that P. chrysosporium and G. oregonense were among the most sensitive species while I. dryophilus and T. versicolor were more tolerant species, having lethal dosages of 17-34, 25-50, >41, and >85 μg-PCP/mg-biomass, respectively. Extracellular enzymes produced in shallow batch cultures by P. chrysosporium and T. versicolor, degraded up to 50% and 75% of the PCP, respectively, when 40 mg-PCP/L was added to mycelia free culture broth. The pattern of chloride ion release resulting from dehalogenation of PCP was bimodal for both species. PCP was degraded by 10 species when PCP was added to whole cultures. Further testing with 4 species showed P. chrysosporium and T. versicolor were the more efficient at reducing aqueous organic chlorine concentrations. Trametes versicolor consistently dehalogenated the most PCP with over 60% of the chlorine being released as chloride ion in 8 days. Comparisons of PCP degradation between species growing as fixed films in rotating tube reactors (RTRs) verified this observation. Degradation in RTRs was superior to degradation in shallow batch reactors on the basis of PCP removal, organic chlorine reductions, and dehalogenation.