Biobleaching of hardwood kraft pulp with cellulasedeficient mutant from hyper ligninolytic fungus izu- 154

Protoplasts of the monokaryotic strain from hyperligninolytic fungus IZU-154 were treated with UV irradiation, and the regenerants were screened for their inability to degrade Walseth cellulose (WC) and carboxymetylcellulose (CMC) on an agar plate. From 2700 regenerants, cellulase deficient and noncellulase mutants were isolated and designated Cel-139 and Cel-145, respectively. Cel-139 showed 15% Avicelase, 60% CMCase, and 10% β-glucosidase activities; however, it retained the same level of lignin degrading capability and manganese peroxidase (MnP) production when compared with wild-type IZU-154. On the other hand, Cel-145 showed deterioration in lignin-degrading capability, despite a substantial level of MnP production. Furthermore, biobleaching of hardwood kraft pulp (HWKP) by wild-type IZU-154 and Cel-139 in the solidstate fermentation system, without supplemental nutrients, were investigated. After 5 d of treatments with both fungi, pulp brightness increased from 33 to 65% ISO brightness, and Kappa number decreased from 13.9 to 6.0. However, yield loss of biobleached pulp was 20% lower with Cel-139 than with wild-type IZU-154.[PUBLICATION ABSTRACT]