The lignosulfonate biodegradation by Chrysonilia sitophila at three different nitrogen concentrations with and without oxygenation was studied. Significant transformation was observed at high nitrogen concentrations (76 mmol N/L) in the absence of oxygen flushing as observed by changes in the absorbance, fluorescence, and mol wt distribution. Phenoloxidase production was 1.8 U/L (o-dianisidine oxidation), and the maximum H2O2 (necessary to the action of peroxidase) production was obtained at 12th d in high nitrogen, oxygenated cultures. The pattern of the LS depolymerization was different with and without oxygenation. IR analysis of biodegraded LS showed a relative increase of sulfonate groups, compared with aromatic groups. A decrease of lignosulfonate was evident by the nitroso method.302185192