Laccase-peroxidase synergy modifies Kraft lignin structure and enhances the electrospinnability for bio-based materials.

From the paper

Abstract

Lignin is a promising renewable macromolecular feedstock for advanced carbon-based materials; however, its intrinsic molecular heterogeneity, relatively low molecular weight, and limited thermal stability often hinder direct fiber formation. This study demonstrates that a multienzymatic oxidative system, integrating laccase (O₂-driven, 6.8 × 10⁵ U L⁻¹), manganese peroxidase (Mn3+ shuttle, 1.5 × 10³ U L⁻¹), and lignin peroxidase (high redox potential, veratryl alcohol-free, 3.0 × 10⁴ U L⁻¹),effectively expands the electrospinnability window of Kraft lignin (KL). The redox-diverse enzymatic cocktail, LADEBIO-Pys, produced by Pycnoporus sanguineus through submerged fermentation followed by tangential-flow ultrafiltration(85-98% rejection; up to 140% yield; ∼90% efficiency), promoted radical-mediated oxidative modifications of KL. Enhanced performance was observed upon supplementation of manganese peroxidase from Phanerochaete chrysosporium, at a combined protein loading of 10 mg g⁻¹, revealing synergistic interactions (Colby factor = 1.25). At increased enzymatic loading (30 mg g⁻¹), the LADEBIO-Pys cocktail led to significant shifts in molecular weight distribution, with Mw and PDI increases exceeding 150% and 110%, respectively, comparable to those obtained with commercial Trametes versicolor laccase. Spectroscopic analyses (FTIR and 1H NMR) revealed changes in hydroxyl, methoxyl, and carbonyl-associated regions consistent with oxidative modification of lignin, while thermal analyses (TGA and DSC) indicated alterations in thermal behavior associated with structural reorganization of the lignin macromolecule. As a direct consequence of these enzymatic modifications, KL was rendered electrospinnable, yielding continuous, bead-lean nanofibrous mats (∼0.20 μm) under mild processing conditions. Electrospinning thus served as a functional indicator of lignin processability, highlighting fungal oxidative enzyme cocktails as a scalable strategy to tailor technical lignin for advanced carbon materials and bio-based polymer applications.