Transformation of macromolecules from a brown coal by lignin peroxidase

Indirect evidence has suggested that lignin peroxidase (LiP) of the white-r ot fungus Phanerochaete chrysosporium catalyses oxidative decolourisation a nd depolymerisation of macromolecules from brown coal in vivo. In this stud y we show that LiP catalyses these transformations in vitro. Unmethylated ( USC45 coal) and methylated (MWSC6 coal) fractions of solubilised macromolec ules (M-r > 30 000) from a brown coal were treated with a semi-purified pre paration of LiP isozymes from P. chrysosporium. Both coal fractions were de colourised, losing between 26% and 39% of their absorbance at both 280 nm a nd 400 nm, in reactions that had an absolute requirement for H2O2 and verat ryl alcohol. Neither coal fraction was transformed when the enzyme was heat -inactivated or in the presence of the LiP inhibitor metavanadate. Gel-perm eation chromatography showed that MWSC6 coal but not USC45 was depolymerise d and yielded low-molecular-mass (M-r < 30 000) fragments. Nine monomeric p roducts were identified by GC-MS.