Biopulping of pine wood chips for production of kraft paper board

Pitch is a general term for the low molecular weight, oleophilic materials extracted from wood, which cause a number of technical problems during pulp and paper processing and decrease pulp and paper quality. Furthermore, due to its high toxicity they are also responsible for severe environmental problems when present in the mill waste waters. Pine wood is used by PORTUCEL TEJO mill at Vila Velha de Rodão (Portugal) to produce kraft pulps and contains very high levels of extractives. Wood extractives are mainly composed by triglycerides, sterols, sterol esters, resin acids and fatty acids. As pitch deposits are mainly composed by triglycerides, lipolytic enzymes can be used for reduction of the pitch problem either on hydrolysing the triglycerides on pulps after chemical or mechanical pulping, or inoculating the wood chips using the lipolytic fungi before pulping. Screening of new fungi for application to both depitching and biopulping of pine wood chips was done for fungal strains exhibiting both lipolytic and ligninolytic activities Pleurotus ostreatus, Ceriporiopsis subvermispora and a new isolate named B 33/3 were among the strains selected. Production of ligninolytic enzymes is presented. Pleurotus oestreatus was selected for the application study. Effectiveness of pine wood chips biotreatments done under several incubation conditions was measured as the decrease in extractives in dichloromethane. The fungal treatment reduced in more than 40% the extractives of pine wood and could produce this result in a shorter time than the wood native microflora.