CONTINUOUS PRODUCTION OF MANGANESE PEROXIDASE BY PHANEROCHAETE-CHRYSOSPORIUM IMMOBILIZED ON POLYURETHANE FOAM IN A PULSED PACKED-BED BIOREACTOR

The bottleneck of the application of manganese peroxidase (MnP) on an industrial scale in pulp biobleaching or in degradation of hazardous c ompounds is the lack of an efficient production system. Three main pro blems arise for the continuous production of MnP during secondary meta bolism of Phanerochaete chrysosporium: enzyme production occurs only u nder specific physiological conditions corresponding to C or N limitat ion, high O-2 tension, and adequate Mn+2 concentration; the enzyme tha t is produced is destabilized by extracellular proteases; and excessiv e growth of the mycelium blocks effective oxygen transfer. To overcome these drawbacks, continuous production of MnP was optimized by select ing a suitable bioreactor configuration and the environmental and oper ating conditions affecting both enzyme production and stability. The c ombination between a proper feed rate and the application of a pulsati on in a packed-bed bioreactor permitted the maintenance of continuous secretion of MnP while limiting mycelial growth and avoiding bed clogg ing. Environmental factors as an Mn+2 concentration of 5000 mu M and h igh oxygen tension enhanced MnP production. The hydraulics of the bior eactor corresponding to a plug flow model with partial mixing and an o perating hydraulic rentention time of 24 h were optimal to achieve sta ble operating conditions. This policy allowed long operation periods, obtaining higher productivities than the best reported in the literatu re. (C) 1997 John Wiley & Sons, Inc.