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 composition on the production of lignin peroxidase (LIP) by Phanerochaete chrysosporium immobilized in polyurethane foam in a packed bed bioreactor 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 system (higher recycling ratio) to an almost typical plug flow (no recycling now). The best results corresponded to the bioreactor operating at plug flow with partial mixing. Direct oxygenation to the bioreactors instead of introducing oxygen solved in the feeding stream allowed the LIP synthesis to be favoured. Finally, a feeding strategy maintaining a residual glucose concentration in the bioreactor during the production phase enhanced LIP stability as the production of proteases was minimized. After selecting the best conditions, lignin peroxidase production in packed bed bioreactors operated at alternating growth-production cycles was achieved for 25 days obtaining an overall activity of 6136 U.