Biodegradation of Pentachlorophenol in Aqueous Extract from PCP-Treated Wood by Arthrobacter sp.

Abstract

A process combining aqueous extraction and microbial degradation of pentachlorophenol (PCP) was investigated as a means to reduce the toxicity of treated wood waste. Batch experiments were conducted with mineral salts medium containing pure PCP and with wood leachate obtained from an aqueous extraction of PCP-treated wood. The results indicate that Arthrobacter sp. (ATCC 33790) is able to utilize PCP as the sole carbon source and mineralize it to chloride and carbon dioxide in both pure PCP medium and in wood leachate. In pure PCP medium and in wood leachate, 56–67% and 53–56% of [14C]PCP was recovered as 14CO2, respectively. The specific rates of PCP degradation per cell, measured during the active disappearance of PCP, were an order of magnitude lower in wood leachate than in the pure PCP medium, while the overall rates of degradation were only about three times lower. The specific rate of PCP degradation per viable cell at an initial PCP concentration of 50 mg/L was 4.1×10−10 ±2.1×10−10 mg PCP/viable cell.h. The rate was comparable to those reported for other PCP-degrading organisms, Flavobacterium sp. and Pseudomonas sp. The effect of recycling Arthrobacter from old media to fresh media was also examined. In both pure PCP medium and wood leachate, the specific rates of PCP degradation were approaching constant values and the lag phases became negligible, which showed that during recycling, Arthrobacter became acclimated to PCP. Toxicity experiments using a Microtox test determined that Arthrobacter reduced the toxicity of wood leachate 5–10 times when it degraded PCP.