Manganese peroxidases were overproduced by Phanerochaete chrysosporium I-1512 immobilized on nylon net in a bubble-column reactor. This study investigates a new design of bioreactor, a compromise between a pneumatic reactor and an immobilized biofilm reactor. The carrier, a sheet of nylon net, was maintained by a cylindrical stainless-steel frame installed vertically. It was characterized by its hydrophilic nature, its surface morphology and its surface roughness. P. chrysosporium adhesion was highly efficient; mycelial hyphae invaded the tridimensional structure and strengthened the bonding to the network, as shown by electron scanning microscopy. High levels of Mn peroxidases were produced by strain I-1512 under conditions of glycerol and nitrogen sufficiency when the medium was supplemented with phospholipid and veratryl alcohol. Yields of 3600rU/l Mn peroxidase were produced after 95rh of incubation, indicating significant productivity for industrial purposes (900rU day-1 l-1).