Enzyme membrane reactor system (EMRS) for the bioconversion of lignin-containing substrates by a novel heme peroxidase

The modification and valorization of industrial/technical lignins to new value added, aromatic bioproducts has a great market potential, but is still poorly understood and therefore the integration into broader industrial processes, i. e. biobased product industry, remains a challenging multidisciplinary task. Homogeneous catalysis in an enzyme membrane reactor system (EMRS) featuring a continuous stirred-tank reactor and an external ceramic crossflow ultrafiltration (UF) membrane is a promising approach, particularly when combined with ligninolytic heme peroxidases (POXs) as biocatalysts like the newly crude versatile peroxidase (VP) from Bjerkandera adusta focused in this work. However, time dependent irreversible VP inactivation caused by the enzymes co substrate H₂O₂ and the fouling of the UF membrane are limiting factors. To facilitate mathematical modeling and a rational bioprocess development, separate investigations were carried out studying H₂O₂ related VP (inactivation) kinetics and the UF performance of 2 and 20 kDa tubular ceramic membranes. Including the limiting factors the optimum EMRS productivity and hydraulic retention time are finally evaluated by computer-aided process simulations using a 5 kDa UF membrane operating at optimum flux. Because oxygen utilization is characteristic of normal POX reaction cycles, simple continuous online measurements of dissolved oxygen concentration were very useful to monitor VP inactivation and therefore any H₂O₂ excess.