New Developments and Further Improvements of Hydrolase Mediated Oxidative Delignification and Bleaching of Pulp, 2000 Pulping / Process & Product Quality Conference Proceedings

H. P. Call--Some enzymatic systems for bleaching/delignification of pulp have been discovered in the past, including the mainly indirectly delignifying xylanase system and the mainly directly delignifying systems such as the MnP-systems and the laccase mediator system (1-9). In spite of the fact that these real delignification concepts remain very promising approaches to the delignification and bleaching of pulp only the xylanase bleaching aid system has been industrially implemented so far.

The main idea regarding the development of this new delignification and/or bleaching concept - we have recently made known- was the mimicking a known chemical pulping or bleaching system using an enzymatic method which would be cost competitive and environmentally safe. The major components of this new system are: hydrolases ( e.g. lipases), fatty acids, special environmentally-

safe ketones ( both normally used in the food and cosmetic industry) and H2 O2 . The new system may be able to generate active oxygen species such as e.g. dioxiranes etc. (depending on optimal concentrations of the system components and reaction conditions).

Experiments with different pulp types like sulfate pulp (softwood, hardwood) or sulfite pulp (softwood, hardwood) and annual plants have been carried out under the following treatment conditions: a consistency range of 8 to 14%, a temperature range of 45 degrees C to 65 degrees C, a pH range of 4 to 10 (depending on type of hydrolase used) and a retention time of 1 to 4 hours. The results clearly indicate that one can attain (depending on pulp type and pretreatments, e.g. O2 - delignification etc.) a delignification rate up to 45% with the potential for further improvements and optimizations.