Enzymatic synthesis of kraft lignin-acrylate copolymers using an alkaline tolerant laccase

Funding Information: This study was funded by the Government of Ontario for the project “Forest FAB: Applied Genomics for Functionalized Fibre and Biochemicals” [grant number ORF-RE-05–005], the Natural Sciences and Engineering Research Council of Canada for the Strategic Network Grant “Industrial Biocatalysis Network”, and Genome Canada for the LSARP project “SYNBIOMICS—Functional genomics and techno-economic models for advanced biopolymer synthesis” [grant number 10405] to E.R.M, and US Department of Energy (DOE) EERE under contract no. DE-EE0008148. Publisher Copyright: © 2022, The Author(s). ; Softwood kraft lignin is a major bioresource relevant to the production of sustainable bio-based products. Continued challenges to lignin valorization, however, include poor solubility in organic solvents and in aqueous solutions at neutral pH. Herein, an alkaline tolerant laccase was used to graft acrylate functionalities onto softwood kraft lignin, which is expected to enhance the reactivity of lignin with isocyanate when producing bio-based polyurethanes. Proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and high-performance liquid chromatography were used to confirm successful grafting of the acrylate monomer onto lignin and verify the importance of including tert-butyl hydroperoxide as an initiator in the grafting reaction. Laccase-mediated grafting of softwood kraft lignin under alkaline conditions produced lignin products with approximately 30% higher hydroxyl value and higher reactivity toward isocyanate. The reported enzymatic and aqueous process presents an opportunity for the sustainable valorization of softwood kraft lignin. ; Peer reviewed