This work reports the effect of fungal pretreatment of sugarcane straw in the performance of the treated pulps. Fermentation time, fungal mycelium load and pretreatment scale were studied in the fungal treatment, and the best conditions were 15 days with 250 mg kg(-1) fungal mycelium per straw weight causing high lignin decomposition. At the largest scale tested (50 g straw) lignin degradation exceeded cellulose degradation by 2.4-fold. Acetosolv pulping was carried out in a tank reactor at 120 degrees C The pulping kinetics showed that for biopulps the final lignin content was around 7.5% with a reduction of 40% in the pulping time to reach 12.5% pulp lignin, besides the factorial design showed that the biological pretreatment had a positive effect on the acetic acid reduction (21.5 wt.%) during pulping process. (C) 2008 Elsevier Inc. All rights reserved.