Biological modification of loblolly pine chips with Ceriporiopsis subvermispora prior to kraft pulping

The ability of the white-rot fungus Ceriporiopsis subvermispora to selectively degrade lignin in loblolly pine chips and the effect on kraft pulps was investigated.; The effect of fungal treatment was assessed by comparing changes in untreated wood chips with chips incubated for two and four weeks. The kraft pulping step included two different cooking times and two levels of chemical dosage as the variables, 16 and 22% for the effective alkali and 60 and 90 min at 170°C. The other cooking variables were kept constant for all the experiments and were: sulfidity, 22%; liquor/wood ratio 4:1; time to T_max 90 min.; T_max 170°C.; Scanning electron microscopy (SEM) revealed that the colonization introduced significant chemical and physical changes. Pore size distribution analyses revealed a statistically significant increase in the average pore size as fungal treatment progressed.; Significant reduction in the extractives content (23%) was found in the first 2 weeks, after which the reduction leveled off. Lignin losses reached 2% in the first 2 weeks of incubation, followed by an 11% loss after 4 weeks of treatment. Lignin phenolic hydroxyl groups increased 14% after 4 weeks of incubation. Fungal treatment caused 4 and 6% carbohydrate loss in 2 and 4 weeks-treated chips, respectively.; The selectivity of the fungal treatment was emphasized in the subsequent kraft pulping. The best response regarding improved delignification was found in kraft pulps processed at the mildest pulping conditions without affecting pulp viscosity.; Benefits of fungal treatment regarding freeness of kraft pulps were evidenced after 4 weeks of incubation with a maximum of 35% freeness reduction in kraft pulps refined at 12,000 rev in a PFI mill. Strength properties of kraft pulps of fungal treated chips were superior to those of the control.; This method involves chemical and physical modification of wood chips using fungi. The approach improved chip impregnation, which in turn, led to more uniform kraft pulping. Transformation of raw material is one of the means of improving the production of chemical pulps.