2-STEP DEGRADATION OF PYRENE BY WHITE-ROT FUNGI AND SOIL-MICROORGANISMS

The effect of soil microorganisms on mineralization of C-14-labelled p yrene by white-rot fungi in solid-state fermentation was investigated. Two strains of white-rot fungi, Dichomitus squalens and a Pleurotus s p. were tested. The fungi were incubated on milled wheat straw contami nated with [C-14]pyrene for 15 weeks. CO2 and (CO2)-C-14 liberated fro m the cultures were determined weekly. To study the effect of soil mic roorganisms on respiration and [C-14]pyrene mineralization in differen t periods of fungal development, the fungal substrate was covered with soil at different times of incubation (after 0, 1, 3, 5, 7, 9 or 11 w eeks). The two fungi showed contrasting ecological behaviour in compet ition with the soil microflora. Pleurotus sp. was highly resistant to microbial attack and had the ability to penetrate the soil. D. squalen s was less competitive and did not colonize the soil. The resistance o f the fungus was dependent on the duration of fungal preincubation. Mi neralization of [C-14]pyrene by mixed cultures of D. squalens and soil microorganisms was higher than by the fungus or the soil microflora a lone when soil was added after 3 weeks of incubation or later. With Pl eurotus sp., the mineralization of [C-14]pyrene was enhanced by the so il microflora irrespective of the time of soil application. With D. sq ualens, which in pure culture mineralized less than did Pleurotus sp., the increase of [C-14]pyrene mineralization caused by soil applicatio n was higher than with Pleurotus sp.