ENZYMATIC TREATMENT WITH MANGANESE PEROXIDASE FROM PHANEROCHAETE-CHRYSOSPORIUM FOR ENHANCING WHEAT-STRAW PULP CHARACTERISTICS

Two wheat straw pulps (Kraft pulp and Chemimechanical pulp (CMP)) were treated with a crude enzymatic extract containing mainly manganese de pendent peroxidase. The extract was prepared from the culture supernat ant of a hypersecretory strain of Phanerochaete chrysosporium. Enzymat ic treatment was applied to an unbleached pulp suspension (2% w/v). La ctate buffer (pH 4.5) was used to regulate the pH at the MnP optimum a ctivity and to stabilize the diffusing oxidative agent (Mn3+). The enz ymatic treatment was applied for 4 hours only, so as to ensure compati bility with industrial processes. After this treatment the kappa numbe r of unbleached Kraft pulp was reduced by about 50% and the consumptio n of bleaching reagent was subsequently reduced to the same extent. As with unbleached CMP, the enzymatic treatment substantially enhanced t he physical properties of the pulps. In all the cases studied, transmi ssion electron microscopy showed that structural changes had occurred in the treated Fibres as compared with untreated samples. The main mod ification appeared to be a superficial defibrillation, which was somet imes accompanied by extensive delamination depending upon the extent t o which the straw had been destructured by previous chemical and mecha nical treatments.