Lignin peroxidase production by the white-rot fungus Phanerochaete chrysosporium is markedly influenced by the buffer system employed. In immobilized P. chrysosporium cultures with carbon-limited glucose medium, the use of acetate buffer resulted in higher lignin peroxidase activities than tartrate. With acetate as the buffer in shake-flask cultures a 20% to over 100% improvement in lignin peroxidase production was obtained as compared to tartrate-buffered systems. Of trace elements, Cu2+, Mn2+ and Zn2+ seemed to have the greatest influence on lignin peroxidase production. Furthermore, an increase in the Cu-2+ and Zn2+ concentrations resulted in considerably higher ligninase activities. Although it has been shown previously that high manganese levels repress ligninase production, for maximum ligninase production the presence of some Mn2+ appeared to be necessary. The concentration of phosphorus had surprisingly little effect on ligninase production. Highest lignin peroxidase activities were obtained with lower phosphorus concentrations, but reasonably high activities were obtained within the whole studied phosphorus range of 0.12-4.60 gl(-1). Diammonium tartrate alone was a better nitrogen source than a mixture of diammonium tartrate, proteose peptone and yeast extract. The addition of solid manganese(IV)oxide to 3-day-old immobilized biocatalyst cultures increased the maximum ligninase activity obtained by about one-third.