Development of Immunomicroscopic Methods for Bioremediation

Abstract

In nature, wood can be completely degraded by lignolytic fungi. Basidiomycetous white-rot fungi are particularly efficient wood degraders because of their ability to completely mineralize lignin [1,2]. The enzymes produced by white-rot fungi are directed against the two types of macromolecules that make up the walls of wood cells, Polysaccharides and polyphenols.. These enzymes consist of Polysaccharide hydrolases that break down cellulose and hemicelluloses, and of a series of oxidizing enzymes that are able to attack and depolymerize lignins. The latter group consists of a variety of extra-cellular enzymes among which peroxidases — principally lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) — together with phenol oxidases laccase (Lac), aryl-alcohol oxidase (AAO) and other nonphenol oxidases, contribute to the highly complex mechanisms leading to lignin depolymerization, aromatic rings opening and demethylation [3, 4, 5]. An essential step in the enzymic attack of lignin is the formation of aryl cation radicals originating from both phenolic and nonphenolic aromatic rings [1, 4, 6]. This is the typical mode of action of LiP which uses hydrogen peroxide to generate aryl cation radicals. The other major peroxidase, particularly efficient in lignin oxidation, is manganese peroxidase which oxidizes manganese ions from Mn+2 to Mn+3. These ions that have a short life-time, are stabilized by organic acids, mostly dicarboxylic acids, and are thought to diffuse in the tight lignocellulosic network of the wood cell walls [7]. Another component of the enzyme complex participating in lignin oxidation is laccase, a phenol oxidase which seems now to be rather widespread amont the most efficient wood-degrading white-rot fungi [8].