New developments in enzyme-assisted delignification and bleaching

摘要

The paper focuses on new applications of certain hydrolases, mainly lipases, in an enzyme-assisted oxidizing system useful e.g. for delignification/bleaching of pulps, the so-called hydrolase mediated oxidation system (HOS). This new system has as its main components: lipases, special fatty acid compounds, special ketone compounds and peroxides. The paper also focuses on new approaches to delignify or to bleach pulp with a new class of oxidation systems of enzymatically-generated redox agents in situ: reactive oxygen species (ROS) or reactive nitrogen species (RNS). These reactive ROS or RNS species (radicals, ions or reactive compounds) are produced in combination with H_2O_2 or superoxidc from precursors which are able to release NO, NO~+ and/or NO~-, dicyclopentadienyl transition metal complexes (mainly iron complexes) or special sulfur compounds or activated sulfite which can react with ketones to form dioxirane or similar types of compounds.