DEGRADATION OF POLYCHLORINATED-BIPHENYLS BY WHITE-ROT FUNGI PLEUROTUS-OSTREATUS AND TRAMETES-VERSICOLOR IN A SOLID-STATE SYSTEM

An industrial PCB-isomer mixture, made up mainly of tri- and tetra chl orinated biphenyls, were loaded on wood chips and incubated with Pleur otus ostreatus and Trametes versicolor. After only 5 weeks the PCB mix ture was degraded more than 95%. Penta- and hexachlorbiphenyls are als o found to be degradable by more than 50%, depending on their substitu tion pattern. Only 2,2',4,4',5,5'-hexachlorbiphenyl (Ballschmiter No. 153) was resistant to degradation. Contaminant concentrations ranged f rom 100 ppm to 650 ppm for single isomers and 2500 ppm for all PCBs. P hanerochaete chrysosporium was not able to degrade any PCB except mono - and dichlorbiphenyl in a solid state system under normal oxygen leve ls. Lignosulfonate, an inducer of lignolytic activity, had no effect o n the degradation of PCBs with Pleurotus ostreatus or Trametes versico lor. Malt medium supported the growth of fungus and could also be repl aced by potato pulp. An oxygen concentration of 10% inside the substra te combined with 10% CO2 had no influence on the degradation potential of Pleurotus ostreatus. Mixing the wood chips with loamy soil did not affect the degradation process of PCBs. However, direct application o f xenobiotics to the soil prior to mixing with wood chips greatly redu ced the speed of their degradation. After 7 weeks, only 50%-60% of the degradation obtained on wood chips were observed in this system, in s pite of the fact that the overall composition of the solid state syste m was identical. The present study demonstrates in general that the el imination of these recalcitrant substances is possible in wood and soi l samples. The lower rate of PCBs degradation in soil may be due to ge neral lowered bioavailability of contaminants.