Novel aspects in the enzyme-based transformation of polyphenols

The biotechnological conversion of lignocellulosic biomass is an interesting option within the development and refinement of biorefinery processes. While the use of enzymes for cellulose conversion is essentially matured, enzymatic (downstream) valorisation of lignins using enzymatic processes continues to pose challenges. When thinking of lignocellulosic enzymes for such processes, the mentioned challenges derive from a lack of control of polymerisation/re-polymerisation, loss of enzymatic activity due to adverse environments generated by the compromise between enzyme needs and lignin solubility, enzyme inhibition, etc. Some of these challenges can eventually be circumvented rethinking the set-up for doing enzymatic lignin transformations. One aspect of such a rethinking could involve the use of more dynamic reaction settings, avoiding long contact times between enzyme and the products they have formed. This can be eventually facilitated going for flow chemistry principles, applied to the enzymatic lignin transformation. We present here results obtained for the use of some commercially available laccases (EC 1.10.3.2), treated in various modes to be used in a flow chemical setting for downstream lignin valorisations, including degradation and functionalisation. The presentation will highlight the challenges encountered and connected with enzyme manipulation and the incorporation of immobilised enzymes in experimental flow reactors. Scope and limitations of this approach are presented using targeted example transformation, and obtained results will also be discussed in light of process- and set-up-dependent kinetic aspects.