Controlled Seasoning of Scots Pine Chips Using an Albino Strain of Ophiostoma

Traditional seasoning of wood chips normally results in significant yield losses and brightness reduction due to the uncontrolled action of microorganisms. Techniques for reduction of the amount of wood extractives with minimal yield and brightness loss are therefore of interest for the pulp and paper industry. To study a biotechnological approach for reduction of wood extractives, wood chips from sapwood of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were treated with a commercial albino strain of the sap stain fungus Ophiostoma piliferum. During 2 weeks of controlled seasoning, the content of wood extractives decreased by approximately 40% for Scots pine and 25% for Norway spruce, where the triglyceride contents were degraded to a greater degree. Thermomechanical pulps were produced from untreated and pretreated pine chips. The properties of these pulps and corresponding laboratory sheets were investigated. The pretreated pulps showed less shortened fibers, lower amounts of triglycerides, and enhanced strength properties. The mechanisms behind these effects are discussed. Furthermore, the ability of the albino Ophiostoma piliferum to displace mould growth from wood chips was investigated in a series of experiments. It was concluded that the fungus should preferably be inoculated on fresh chips in order to repress mould growth.