Path Forward to Practical Nascent Laccase Biobleaching Technologies, 2000 Pulping / Process & Product Quality Conference Proceedings

F. S. Chakar, L. Allison, D. H. Kim, A. Ragauskas--The advantages of chemical bleaching agents are well established and include many factors such as ease of use, reliability, acceptable selectivity, and bleaching costs. Given these considerations, the successful implementation of a biobleaching stage in a modern kraft mill must meet several criteria including cost, dependability, and pulp performance properties. Research studies into the biobleaching of kraft pulps promise new bleaching technologies that could reduce capital expenditures and yield bleached products with superior physical pulp properties and negligible impact on the environment.

Over the past several years, the utilization of laccase-mediator systems (LMS) for delignifying kraft pulps has steadily improved in terms of delignification capabilities, enzyme and mediator dosages, and bleached pulp properties. Our studies have been primarily directed at understanding the fundamental chemical processes involved in this biodelignification process. A better understanding of the enzymatic and chemical mechanisms involved in the LMS system will improve the overall biobleaching effect and hasten its application in commercial bleaching operations. This paper reports on improving the LMS system using violuric acid (VA) or N-acetyl-N-phenyl-hydroxylamine (NHA) as mediators. The bleaching properties of LMS were investigated in terms of brightness, lignin content, and pulp viscosity.