Lignin blending modulates laccase-catalyzed polymerization of lignosulfonates using organosolv lignin from vine...

Laccase-catalyzed repolymerization of technical lignins is an emerging biocatalytic strategy for upgrading lignin streams into polymeric systems and biomaterial precursors under mild reaction conditions. Lignosulfonates are attractive substrates for enzymatic polymerization due to their high water-solubility; however, their relatively low reactivity can limit their application. In contrast, organosolv lignin typically presents low-molecular weight and high phenolic content, which increase its susceptibility to laccase-mediated oxidation; however, its limited water solubility restricts enzymatic processing. In this work, lignin blending was evaluated as a strategy to modulate laccase-catalyzed polymerization by combining lignosulfonates (LS) with organosolv lignin from vine shoots (LVS). The effect of LVS incorporation on enzymatic oxidation was investigated through oxygen consumption measurements, viscosity evolution, molecular weight analysis and characterization of LS-based films. The presence of LVS modified oxidation kinetics, leading to prolonged oxidative activity, accelerated viscosity development and higher apparent molecular weight fractions at shorter reaction times compared to LS alone. LS-LVS films were produced to evaluate whether blending affected material surface properties. FTIR analysis supported structural changes consistent with oxidative coupling, while water contact angle measurements showed increased surface hydrophobicity in LS/LVS systems. Overall, the results demonstrate that blending lignins with different structural features can modulate enzymatic polymerization and influence the properties of LS films. This work highlights lignin blending as a simple biocatalytic strategy to modulate laccase-catalyzed polymerization and upgrade heterogeneous lignin streams toward lignin-based biomaterials within biorefinery concepts.