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Modeling the design and operational mode of a continuous membrane reactor for enzymatic lignin modification

: Busse, N.; Kraume, M.; Czermak, P.


Biochemical engineering journal 124 (2017), pp.88-98
ISSN: 1369-703X
Journal Article
Fraunhofer IME ()

The modification of lignin-derived compounds such as technical lignins, which are highly aromatic and therefore valuable as renewable feedstocks for the biobased product industry, is still a challenging and multidisciplinary task. An enzyme membrane reactor system (EMRS) featuring a continuous stirred-tank reactor and an external ceramic crossflow ultrafiltration membrane is a promising configuration, particularly when combined with ligninolytic heme peroxidases (PODs) as biocatalysts, such as the new versatile peroxidases (VP) described herein. However, time-dependent irreversible enzyme inactivation caused by the co-substrate H2O2 and the fouling of the filtration membrane are limiting factors. To facilitate rational bioprocess development and reactor design, we present an overall modeling concept for a continuous operating mode that addresses both limitations. When including H2O2-related VP inactivation dynamic model analyses showed that two H2O2 molecules were required to convert one molecule of the reducing substrate (here, adlerol). In this context, an (initial) enzyme inactivation rate k(i)(0) caused by factors other than H2O2 (e.g. the used buffer system) was introduced. Because oxygen utilization is characteristic of normal POD actions, the continuous online measurement of dissolved oxygen concentration was useful to monitor enzyme inactivation and therefore an excess of H2O2.