BIOBLEACHING OF HARDWOOD KRAFT PULP WITH CELLULASE-DEFICIENT MUTANT FROM HYPER LIGNINOLYTIC FUNGUS IZU-154

Protoplasts of the monokaryotic strain from hyperligninolytic fungus I ZU-154 were treated with UV irradiation, and the regenerants were scre ened for their inability to degrade Walseth cellulose (WC) and carboxy metylcellulose (CMC) on an a,oar plate. From 2700 regenerants, cellula se-deficient and noncellulase mutants were isolated and designated Cel -139 and Cel-145, respectively. Cel-139 showed 15%, Avicelase, 60% CMC ase, and 10% beta-glucosidase activities; however, it retained the sam e level of lignin degrading capability and manganese :peroxidase (MnP) production when compared with wild-type IZU-154. On the other hand, C el-145 showed deterioration in lignin-degrading capability, despite a substantial level of MnP production. Furthermore, biobleaching of hard wood kraft pulp (HWKP) by wild-type IZU-154 and Cel-139 in the solid-s tate fermentation system, without supplemental nutrients, were investi gated. After 5 d of treatments with both fungi, pulp brightness increa sed 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 C el-139 than with wild-type IZU-154.