Manganese peroxidases (MnP) from Phanerochaete chrysosporium and Bjerkandera sp. BOS55 were immobilised in glutaraldehyde-agarose gels. Four different strategies were considered concerning the activation of the support (low or high density) and the ionic strength (low or high). In terms of immobilisation rate and yield, better results were obtained when low ionic strength conditions and high density activated support (75 muEq/ml) were used. Immobilisation proceeds initially with an ionic adsorption which facilitates the further covalent attachment of the enzyme to the support. An almost complete immobilisation has been attained in a very short period (0.5-2 h). Immobilisation maintained a high percentage of MnP activity for long periods of time (activity levels of 50-60% after more than I year at room temperature storage). Other desirable effects such as increased thermostability at 50-60 degreesC for MnP from Bjerkandera and higher resistance to high H2O2 concentrations for MnP for R chrysosporium were also obtained. This latter is quite an interesting feature because it avoids the inactivation of the enzyme in the presence of an unbalanced concentration of H2O2. The improved characteristics of the immobilised MnP make its application in several fields such as the enzymatic oxidation of hardly degradable compounds more feasible. (C) 2003 Elsevier Science Inc. All rights reserved.