Utilization of the Phanerochaete chrysosporium ligninolytic system and the potential for toxaphene degradation

Abstract

The idiophasic production of nonspecific extracellular enzymes by the Basidiomycete fungus Phanerochaete chrysosporium, referred to as the ligninolytic system, has been reported by many researchers to be capable of degrading a broad spectrum of environmentally persistent compounds including some alkyl halide chemicals. Cultivation of the fungus and the ability of the ligninolytic system to degrade the alkyl halide pesticide toxaphene were explored in pure liquid cultures. The effects of culture growth temperature and toxaphene concentration were evaluated. The extent of toxaphene conversion with time was determined using three different indicators; toxaphene gas chromatographic elution patterns, the determination of free chloride concentrations by ion chromatography analyses, and the distribution of chloride in aqueous and biomass fractions via total organic halide analyses. Oxidation of the azo dye, Orange II, via spectrophotometric measurements was employed to determine the activity and reactivation of the fungal ligninolytic system.

Degradation of toxaphene in the P. chrysosporium cultures was limited, with a maximum of 7% of the original mass of chloride originating from the toxaphene being released over a three week period. The main removal mechanism of the toxaphene from solution was observed to be adsorption to the mycelium biomass. Ligninolytic activity was equally active at temperatures less than optimum for maximum growth of the fungus which implies that the ligninolytic system can be effective with reduced temperature requirements. Elevated pH conditions did not effect ligninolytic activity indicating that high more neutral pHs, which are characteristic of soil properties, do not inhibit ligninolytic activity. Reactivation of the ligninolytic system was accomplished in a nonimmersed liquid culture system. The immobilized configuration appeared to be an effective system for cultivating the ligninolytic system on a continuous basis.