Fast methods for the identification of suitable chemo-enzymatic treatments of Kraft lignin to obtain aromatic compounds

Kraft lignin valorization is the cornerstone for the establishment of biorefineries based on residual fractions from the pulping processes. From the precipitation process to depolymerization, various strategies have emerged, all focused on obtaining high yields or higher purity monomers. The strategy used in this study was to modify the structure of the precipitated Kraft lignin with different oxidative enzymatic treatments, with the purpose of facilitating subsequent catalytic depolymerization. The treatments were performed with different concentrations of lacasse and mediator, and then lignin structure and chemical composition were analyzed to find the optimal treatment for depolymerization. Chemometric methods based on infrared signals were used as fast tools to reduce the complexity of the chemical information generated from lignin characterization, and were therefore used to distinguish the most appropriate chemoenzymatic treatment. The results of the chemical catalysis showed higher conversion yields of the Kraft lignin after the enzymatic process than after using only chemical catalysis. The primary compounds obtained were catechol and its derivatives, thus validating its selection by means of infrared spectroscopy and chemometrics. In conclusion, it was possible to choose a straightforward chemoenzymatic process that improves the conversion of the Kraft lignin to aromatic compounds with the help of non-destructive, low-cost, and fast tools. (c) 2020 Society of Chemical Industry and John Wiley & Sons, Ltd