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

Contamination of soils and aquifers by aliphatic halocarbons is a serious environmental pollution problem. We report here the novel observation that the halocarbons trichloroethylene (TCE) and CCl4 were mineralized by Phanerochaete chrysosporium under aerobic conditions. Ligninolytic 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 mineralized by nonligninolytic cultures of P. chrysosporium, indicating that lignin peroxidases play an important role in the mineralization of these chemicals. In a previous study, we reported lignin peroxidase-catalyzed reductive dehalogenation of CCl4 with the resultant formation of trichloromethyl radical. We have extended this study and report here reductive dehalogenation of CHCl3, CH2Cl2, TCE, and 1,1,1-trichloroethane. Dehalogenation was catalyzed by a reductive reaction system containing lignin peroxidase, veratryl alcohol, EDTA or oxalate, H2O2, and the halocarbon with phenyl N-tert-butylnitrone as a spin trap for electron spin resonance detection of the resulting radicals. Since all the components of the reductive system with oxalate as an electron donor are excreted by P. chrysosporium, we propose that this mechanism may be involved in the degradation of these halocarbons by the fungus.