Trametes versicolor pretreatment of poplar chips for upgrading kraft pulp

Industrial poplar chips were pretreated for up to 3 weeks by Trametes versicolor and subsequently used for kraft pulping to achieve a constant kappa number of about 20. Pretreated wood chips were characterized using SEM and FTIR analysis. The results showed that the lignin and carbohydrate structures were considerably degraded by fungal pretreatment after 3 weeks and had an influence on kraft pulping and paper properties. Higher chemical charge in pulping, lower fine and higher long fiber fraction, lower viscosity and increased drainage time were observed in pretreated pulp samples. Handsheet properties, such as density, tensile index, burst index and Scott band, were increased up to a 2 weeks pretreatment time and then decreased together with opacity, brightness and tear index with prolonged fungal pretreatment time. SEM images of handsheet cross-section showed more a homogenized profile with increasing pretreatment time.