Conventional kraft pulping using enzyme pretreatment technology : role of diffusivity in enhancing pulp uniformity

Kraft delignification of acetone extracted southern pine chips was enhanced by enzyme pretreatment with a cellulase/hemicellulase/pectinase mixture. The increased delignification was attributed to the enhanced transport processes in wood as a result of enzymatic hydrolysis. The chips were impregnated with the enzyme solutions after vacuum evacuation. Treatment was for 24 h at 50°C and pH 4.8. In chips thicker than 4 mm, enzyme pretreated pulps had higher screened yields than the control pulp. Reject levels of pulps resulting from enzyme pretreatment were lower than resultant pulps from control chips with similar thickness profiles. A kraft pulping model that considers the combined effects of diffusion and chemical reaction was used to simulate the pulping study and predict other final pulp properties. The model results showed that the improvement in pulp uniformity was consistent with the measured increase in diffusivity resulting from enzyme treatment.