EFFECT OF ENDOGLUCANASES AND HEMICELLULASES IN MAGNETIC AND FLOTATIONDEINKING OF XEROGRAPHIC AND LASER-PRINTED PAPERS

Laser-printed paper was treated individually and with combinations of purified endoglucanases from Gloeophyllum sepiarium (EGS) and Gloeophy llum trabeum (EGT), a xylanase from Thermomyces lanuginosus (X) and a mannanase from Sclerotium rolfsii (M). Subsequent toner removal effici ency after enzymatic and both magnetic or flotation deinking treatment was assessed by image analysis. The enzyme effect was more pronounced in magnetic deinking, demonstrating 94% removal of toner using a comb ination of EGS and X. The use of the pure EGT and EGS suggests that en doglucanases are responsible for most of the success in deinking. Comp ared to flotation deinking (89%), a higher yield of fibres (97.2%) was attained with this new combined enzymatic-magnetic technique, which c onsequently uses only tap water and no chemicals. While all enzyme app lications increased freeness and slightly reduced intrinsic fibre stre ngth, the resultant handsheets strength was maintained or marginally i mproved. The nature of the individual endoglucanase seems to play an i mportant role since different deinking efficiencies and strength prope rties were measured with EGS and EGT, which are closely related enzyme s in terms of molecular properties and specificities on model substrat es. (C) 1998 Elsevier Science B.V. All rights reserved.