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Pulp wash was used as substrate for the activity of ligninolytic enzymes of the fungus Pleurotus sajor-caju. Activity of laccase (Lac) and manganese peroxidase (MnP) as well as fungal biomass occurred under four conditions: different pulp wash concentrations, pH variation at the optimal pulp wash concentration, different glucose concentrations, and different concentrations of ammonium nitrate. The best enzyme activity and biomass production were obtained with in natura pulp wash and pH corrected to 5.0 (4884 IU/L Lac; 82 IU/L MnP; 25 g/100 mL biomass). However, the addition of glucose and ammonium nitrate to the pulp wash was not necessary for increasing the enzyme activity and biomass production. Efficient removal of pulp wash chemical oxygen demand (99.66%) and biochemical oxygen demand (83.27%) occurred after the mycoremediation with P. sajor-caju in the optimized conditions. Lactuca sativa L. seeds germination bioassay showed a four-fold reduction in the residue toxicity (EC50 28.72%) after the treatment with the fungus. Our findings are consistent with the notion that pulp wash is an excellent substrate for inducing the activity of ligninolytic enzymes and producing fungal biomass, and that the biological treatment is efficient to reduce effluent toxicity. [ABSTRACT FROM AUTHOR]