Evaluation of bacterial pretreatment of spruce woodchips for mechanical pulping

Properties of woody raw materials for papermaking can be modified by microbial pretreatments. In this work, the growth conditions of a Pseudomonas marginalis strain, which efficiently reduces extractives in Norway spruce, were studied in more detail. Additional nitrogen was necessary for efficient growth of P. marginalis on the chips, whereas the sterilisation of the woodchips was not required for growth and for reduction of extractives content. The effects of P. marginalis pretreatment on the energy consumption in refining and on the paper properties of the pulp produced were investigated. No energy savings in refining were observed, but the tensile strength of the handsheets was improved. Evidently this was due to the removal of extractives in chip pretreatment