LIGNIN-MODIFYING ENZYMES FROM SELECTED WHITE-ROT FUNGI - PRODUCTION AND ROLE IN LIGNIN DEGRADATION

White-rot fungi produce extracellular lignin-modifying enzymes, the be st characterized of which are laccase (EC 1.10.3.2), lignin peroxidase s (EC 1.11.1.7) and manganese peroxidases (EC 1.11.1.7). Lignin biodeg radation studies have been carried out mostly using the white-rot fung us Phanerochaete chrysosporium which produces multiple isoenzymes of l ignin peroxidase and manganese peroxidase but does not produce laccase . Many other white-rot fungi produce laccase in addition to lignin and manganese peroxidases and in varying combinations. Based on the enzym e production patterns of an array of white-rot fungi, three categories of fungi are suggested: (i) lignin-manganese peroxidase group (e.g. P . chrysosporium and Phlebia radiata), (ii) manganese peroxidase-laccas e group (e.g. Dichomitus squalens and Rigidoporus lignosus), and (iii) lignin peroxidase-laccase group (e.g. Phlebia ochraceofulva and Jungh uhnia separabilima). The most efficient lignin degraders, estimated by (CO2)-C-14 evolution from C-14-[Ring]-labelled synthetic lignin (DHP) , belong to the first group, whereas many of the most selective lignin -degrading fungi belong to the second, although only moderate to good [C-14]DHP mineralization is obtained using fungi from this group. The lignin peroxidase-laccase fungi only poorly degrade [C-14]DHP.