PRODUCTION OF LIGNIN PEROXIDASE BY PHANEROCHAETE-CHRYSOSPORIUM IN A PACKED-BED BIOREACTOR OPERATED IN SEMICONTINUOUS MODE

The effect of the hydraulics, the oxygenation and the substrate compos ition on the production of lignin peroxidase (LIP) by Phanerochaete ch rysosporium immobilized in polyurethane foam in a packed bed bioreacto r was studied. The hydrodynamic behaviour of the reactors was modified by selecting different flow recycling ratios (recycling flow/feeding flow), and therefore the flow model ranged from a complete mixed syste m (higher recycling ratio) to an almost typical plug flow (no recyclin g now). The best results corresponded to the bioreactor operating at p lug flow with partial mixing. Direct oxygenation to the bioreactors in stead of introducing oxygen solved in the feeding stream allowed the L IP synthesis to be favoured. Finally, a feeding strategy maintaining a residual glucose concentration in the bioreactor during the productio n phase enhanced LIP stability as the production of proteases was mini mized. After selecting the best conditions, lignin peroxidase producti on in packed bed bioreactors operated at alternating growth-production cycles was achieved for 25 days obtaining an overall activity of 6136 U.