Biobleaching of kraft pulp

This review reviews current research on the application of biotechnology to the bleaching of kraft pulp. Biobleaching research focuses on using white rot fungi, and ligninase and hemicellulase enzymes. Bleaching with white rot is generally very slow and the primary problems appear to be the control of cellulose degradation, the technical aspects of scale up and the avoidance of an initial lag phase. Ligninase enzymes depolymerize lignin and in combination with an extraction stage, partially bleach kraft pulp. Bleaching with hemicellulase enzymes looks promising. A reduced need for active chlorine has been obtained by boosting the bleachability of pulp through pretreatment with hemicellulose hydrolysing enzymes.