Investigation into the biotechnological modification of wood and its application in the wood-based material industry

Because of the growing utilization of renewable raw materials, the technica l use of lignocellulosic fibres from wood and other annual plant materials is becoming increasingly important. The conventional production process of fibreboards is characterized by high-energy consumption and use of ecologic ally insecure synthetic resins. Approximately 40 to 45% of the total energy expenditure are used for the thermo-mechanical pulping. Because of high pl astication temperatures, an inactive lignin crust on the fibre surface is f ormed. For that reason, for glueing of the fibres, urea formaldehyde and me lamin resins are usually used. The costs for the resin amount to approximat ely 50% of the entire material costs. In addition, environmental problems a re caused. The aim of our investigation is the reduction of energy and resi n consumption by enzymatic modification of wood chips and the enzymatic act ivation of the inherent bonding strength of the material. The first industr ial use of fungi for the modification of wood was in the production of "Myc o wood". Pleurothus ostreatus and Trametes versicolor were applied for nons terile delignification of beech wood. The present investigation of the auth ors deals with the mycological pre-treatment of wood chips in order to redu ce the energy consumption during wood pulping. The screening results favour the brown rotter Gloeophyllum trabeum for pinewood (Pinus silvestris) and the white rotter Trametes hirsuta for beech (Fagus silvatica). Both species show resistance against mould fungi. The use of submerged inoculum of thes e fungi has the advantage over wheat inoculum that the lag phase is less th an 12 hours and that the addition of nutrients or fungicides is not necessa ry. Short-time wood chip incubation results in a 40% decrease of energy con sumption during thermo-mechanical pulping and in improved fibreboard proper ties. Lignin reduction could not be determined by gravimetrical and x-ray m icroanalysis. Comparative investigations of fibre incubation using laccase, a submerged c ulture of Trametes versicolor and rape straw fibres show a high increase in bending and tensile strength and an improvement in the hygroscopic propert ies of glue-free fibre boards for the last two incubation kinds. Similar ef fects have been obtained incubating pine wood fibres for the production of fibre sheets with enzyme medium of Trichoderma reseei.