No synergy observed between mannanase and xylanase in enzyme-assisted bleaching modified kraft pulp

MCC (Modified Continuous Cook) kraft pulp, prepared in the laboratory from radiata pine, was treated with various combinations of mannanase and xylanase purified from Trichoderma reesei. The bleachability of these pulps was evaluated using a standard DED bleaching sequence over a range of active chlorine multiples. No synergy was found in the effects of mannanase and xylanase treatments on the bleaching of MCC pulp. In this study, mannanase treatment by itself had very little effect on pulp bleaching even though the expected amounts of mannan were solubilised. This result is inconsistent with previous results, and brings to question the reliability of mannanase-assisted bleaching of MCC pulp. Variability in the laboratory preparation of modified pulps may cause subtle changes in pulp properties that affect their response to enzymes.