REDUCTIVE DEHALOGENATION OF ALIPHATIC HALOCARBONS BY LIGNIN PEROXIDASE OF PHANEROCHAETE-CHRYSOSPORIUM

Contamination of soils and aquifers by aliphatic halocarbons is a seri ous environmental pollution problem. We report here the novel observat ion that the halocarbons trichloroethylene (TCE) and CCl4 were mineral ized by Phanerochaete chrysosporium under aerobic conditions. Ligninol ytic cultures of this white rot fungus mineralized 20.3% of 10 ppm TCE and 18.8% of 10 ppm CCl4 in 9 days. These chemicals were not minerali zed by nonligninolytic cultures of P. chrysosporium, indicating that l ignin peroxidases play an important role in the mineralization of thes e chemicals. In a previous study, we reported lignin peroxidase-cataly zed reductive dehalogenation of CCl4 with the resultant formation of t richloromethyl radical. We have extended this study and report here re ductive dehalogenation of CHCl3, CH2Cl2, TCE, and 1,1,1-trichloroethan e. Dehalogenation was catalyzed by a reductive reaction system contain ing lignin peroxidase, veratryl alcohol, EDTA or oxalate, H2O2, and th e halocarbon with phenyl N-tert-butylnitrone as a spin trap for electr on spin resonance detection of the resulting radicals. Since all the c omponents of the reductive system with oxalate as an electron donor ar e excreted by P. chrysosporium, we propose that this mechanism may be involved in the degradation of these halocarbons by the fungus.