The Role of Manganese in Enhanced Lignin Degradation by Pleurotus Ostreatus

P. osreatus belongs to a group of basidiomycetes, degrading preferentially the lignin moiety in woody tissues. A system enabling the conduction of solid state fermentation in chemically defined medium using inert solid support was developed. Under these conditions we could study fungal growth and activities in the absence of manganese. Mn amendments were found to enhance preferential lignin degradation by P. osreatus as shown by Clignin mineralization versus C-Cellulose mineralization as well as the production of Mn-peroxidase. Plant extractives of peeled cotton branches were also found to enhance lignin degradation by the fungus. Cotton stalks amended with MnSO4 were shown to loose 56% of their lignin fraction. Thus showing the potential of Pleurotus in biopulping of non-woody material. The role of Mn(III) in lignin degradation is studied using EPR spectroscopy and spin-traps. It was shown that Mn(III) cart lead to the formation of reactive peroxy radicals atler one-electron abstraction from keto-acids. This is supported by the obligatory need for oxygen in the reaction. These radicals, can serve as diffusible oxidants. A complete system, performing the first step of ligninolysis could then be the production of Peroxy-radicals in the reaction of Mn(III) and plant extractives in the presence of oxygen.