Structural features of lignin-hemicellulose-pectin (LHP) orchestrate a tailored enzyme cocktail for potential applications in bark biorefineries

Wood bark is a structurally complex by-product of the pulp and paper industry, which focuses primarily on the valorization of structurally more regular wood xylem components. The aim of this study was the elucidation of the less valorised willow wood counterparts (whole bark, inner bark, sclerenchyma bundles, and parenchymatous tissues) by NMR spectroscopic techniques. This allowed a better understanding of the structural features of macromolecular components of bark (i.e. pectin, hemicellulose, and lignin), thus providing a base for a more rational design of the customized biochemical processes prior to chemical processing of bark. This crucial knowledge contributed to the creation of a protocol/decision tool to select tailored enzymes (discarding the slightest substrate binding) for the biological pre-treatment of bark to a state suitable for chemical pulping. Such a protocol/decision-making tool would significantly improve the efficiency of enzyme selection by 60-70% due to the specific catalytic activity of the enzymes involved.