The white-rot fungus, Pycnoporus cinnabarinus, was grown in a 200 L packed-bed bioreactor. The dye, Remazol Brilliant Blue R, was added to the reactor and was rapidly decolourised. The phenoloxidase, laccase, catalysed this process. Laccases isolated from different days in the bioreactor cycle indicated variations in charge to size characteristics. Purified laccase from different days was isoelectrically focused and showed variations in intensities and numbers of bands whilst catalytic activity was retained.