PHANEROCHAETE MUTANTS WITH ENHANCED LIGNINOLYTIC ACTIVITY

In addition to lignin, the white rot fungus Phanerochaete chrysosporiu m has the ability to degrade a wide spectrum of recalcitrant organopol lutants in soils and aqueous media. Most of the organic compounds are degraded under ligninolytic conditions with the involvement of the ext racellular enzymes, lignin peroxidases, and manganese-dependent peroxi dases, which are produced as secondary metabolites triggered by condit ions of nutrient starvation (e.g., nitrogen limitation). The fungus an d its enzymes can thus provide alternative technologies for bioremedia tion, biopulping, biobleaching, and other industrial applications. The efficiency and effectiveness of the fungus can be enhanced by increas ing production and secretion of the important enzymes in large quantit ies and as primary metabolites under enriched conditions. One way this can be achieved is through isolation of mutants that are deregulated, or are hyperproducers or supersecretors of key enzymes under enriched conditions. Through UV-light and gamma-ray mutagenesis, we have isola ted a variety of mutants, some of which produce key enzymes of the lig ninolytic system under high-nitrogen growth conditions. One of the mut ants, 76UV, produced 272 U of lignin peroxidases enzyme activity/L aft er 9 d under high nitrogen (although the parent strain does not produc e this enzyme under these conditions). The mutant and the parent strai ns produced up to 54 and 62 U/L, respectively, of the enzyme activity under low-nitrogen growth conditions during this period. In some exper iments, the mutant showed 281 U/L of enzyme activity under high nitrog en after 17 d.