Maize residues were disintegrated and (i) treated with dild. H2SO4 and NaOH to hydrolyze the cellulose and heated in aq. suspension at 100 degrees C for 3 h or (ii) extruded at 110 degrees C and 140-160 degrees C. The raw material prepd. was fermented by using MeH bacteria without any prodn. of biogas. The fermentation process resulted in changes in the chem. structure of lignin. The content of hydroxyl groups and the ratio of aliph. and arom. structures were higher in fermentation residue than in lignin before pretreament and fermentation. The content of carbonyl groups and the ratio of syringil to guaiacyl structures was changed to a lesser extent.