Depolymerization of straw lignin by manganese peroxidase from Nematoloma frowardii is accompanied by release of carbon dioxide

Manganese peroxidase preparations (MnP) from the white-rot fungus Nematolom a frowardii were able to release directly from C-14-labeled milled wheat st raw (MWS; total lignin fraction) and milled straw lignin (MSL; dioxane solu ble part of MWS). Apart from the formation of (CO2)-C-14, (4-10%) the treat ment of insoluble MWS and MSL with MnP resulted in the formation of water-s oluble C-14-lignin fragments (lignin solubilization, 14-25%). Analyses with gel permeation chromatography (GPC) demonstrated the formation of lignin f ragments with predominant molecular masses around 1 kDa. The extent of MWS mineralization and solubilization was enhanced in the presence of reduced g lutathione (GSH) acting as thiol mediator, whereas MSL mineralization was n ot stimulated by GSH. The principle of direct extracellular mineralization of lignin catalyzed by the MnP system may make a significant contribution t o the formation of carbon dioxide in lignin cellulose containing habitats.