A new high-porosity mullite advanced ceramic material (ACM) having an open pore structure on the micron length scale was evaluated as a monolithic support for enzyme catalyzed reactions. The hydrodynamic properties of ACM monoliths were investigated using residence time distribution (RTD) in gas-liquid Taylor flow and compared with classical cordierite monoliths. The hydrodynamic results show that the liquid phase accesses the entire open volume of the wall and exchanges rapidly with the bulk liquid in the channels. The ACM monoliths were functionalized with polyethylenimine (PEI) and with carbon prepared by different methods in order to provide adsorption sites for lactase from Aspergillus oryzae and lipase from Candida rugosa. These monolithic biocatalysts were tested for activity and stability and compared to similarly prepared biocatalysts employing classical cordierite ceramic monoliths. The use of high-porosity ACM monoliths leads to more stable and more active structured bioreactors. The highly open microstructure of ACM affords good access to catalysts deposited within the walls of a monolith and enables high enzyme loadings. (C) 2004 Elsevier Ltd. All rights reserved.