EFFECT OF MODIFIED KRAFT PULPING ON ENZYME ASSISTED BLEACHING

The effect of modified Kraft pulping was studied in the laboratory by treating radiata pine kraft and MCC pulps with several xylanase and ma nnanase preparations then observing the bleach response with a chlorin e dioxide based DED sequence. MCC pulp contained lower proportions of residual hemicellulose than corresponding kraft pulp, suggesting less xylan redeposition occurred during modified pulping. MCC pulp was also less susceptible to xylanase, but not mannanase, attack. Enzyme treat ments removed only a small proportion (< 11%) of residual fibre bound hemicelluloses, with mannanase treatments giving the lowest levels. As sistance to bleaching was generally lower after enzyme treatment of MC C pulp than Kraft pulp. Results suggested that only specific hemicellu loses located near the fibre surface are likely to be involved in enzy me-assisted bleaching. These hemicelluloses may include redeposited xy lan and galactose rich glucomannan.