Phanerochaete chrysosporium ME-446 cultivated in celluose-based media degraded synthetic lignin to about the same extent in high-nitrogen (24 mM N as asparagine) and low-nitrogen (2.4 mM) media when Tween 80 was employed at 0.15%, and 0.075%, respectively. Under these specified conditions of high C-14-DHP mineralization which occurred after 6 days of cultivation, the amount of lignin peroxidase (113 U l(-1)) in high-N media was much higher than that in low N (17 U l(-1) LiP). in contrast, the Mn-dependent-peroxidase activity was nor affected by the N concentration. Likewise, the total (extracellular plus bound) cellobiose:quinone oxidoreductase activity was of the same order (about 15 to 25 U l(-1)) in both high- and low-N/cellulose-based media. These data suggest that the amount of cellobiose:quinone oxidoreductase/cellobiose dehydrogenase formed is critical for optimal ligninolytic activity and that too high levels of these enzymes may be inhibitory The use of the cellulose-based media has made it possible to observe a wide spectrum of enzymatic activities, including protease activity. The relationship among these enzymes is analyzed in the light of the synthetic lignin degradation.