Voltammetric monitoring of laccase-catalysed reactions of different lignins through oxidative coupling with glucosamine

The ability of laccase to facilitate grafting hydrophilic compounds, namely glucosamine to lignin in acetone/water mixtures aiming to obtain grafted novel lignin derivatives with new functionalities was assayed by cyclic voltammetry. The oxidation properties registered for the oxidative reactions of syringaldazine lignin model compound with glucosamine evidenced that the reaction scan is direct proportional with the redox potential differences between substrate and laccase. A comparative electrochemical activity of lignins on the GCE in absence and presence of the laccase and glucosamine is presented. From the measurements of the coupling reactions currents it was concluded that the addition of glucosamine can lead to a partial loss of the redox activity of lignin phenolic groups and the co-substrate interaction with the lignin surface groups.