A set of new thermophilic and alkaliphilic enzyme, xylanases acting on hemicelluloses and laccases acting on lignin, were discovered by in silico screening of databases or developed by protein engineering. Two patent applications were filed, covering a new xylanase with outstanding extremophilic properties and The best performing enzymes reached pilot or industrial scale production.
Kraft lignins isolated from the black liquors of the consortium pulp mills were enzymatically fractionated with METNINTM lignin refining technology, which combines the depolymerisation of lignin by laccase at alkaline conditions with a cascading membrane operation. Sets of softwood and hardwood kraft lignin-derived fractions with decreasing size and increasing phenol content were produced and chemically characterized.
The lignin fractions were oxypropylated to obtain liquid polyols to be used in the formulations of rigid PU foams, attaining up to 50% substitution of fossil-derived polyols. All the lignin samples were compliant with foaming requirements although some process adaptations are required for industrial implementation depending on the lignin properties.
The new extremophilic laccases and lignin fractions were also tested in the manufacture of Medium-Density Fiberboards (MDF). The extremozymes had a positive effect on energy savings during defibring of wood chips. Lignin fractions were applied as a phenol substituent in the formulation of lignin-phenol-formaldehyde (LPF) resins aiming to reduce the content of fossil-derived chemicals. A deep chemical characterization of the resins provided valuable knowledge of the resin formation process. It was possible to obtain suitable resin formulations with a substantial decrease of phenol and formaldehyde contents to values never obtained in these applications.
In the case of kraft pulp delignification and bleaching, the integration of the new extremozymes (laccases or xylanases) in the bleaching sequence allowed reducing the chlorine dioxide load. In particular, bleaching of eucalyptus kraft pulp at pilot scale with the most extremophilic xylanase enabled to save 25% chlorine dioxide, at higher brightness than that currently obtained at the mill, with concomitant 18% reduction of the organochlorinated compounds released in the effluents, and without affecting pulp mechanical properties.
Highly pure hemicelluloses were extracted from bleached kraft pulps with the aid of extremophilic xylanases. These sugars were chemically modified and evaluated as additives in papermaking, allowing up to 80% energy savings during paper refining and notably improving the mechanical and physical properties of paper sheets when added as paper binders. The paper sheets can be recycled preserving the enhanced properties.
The techno-economic and environmental impact assessment showed that the extremozyme-assisted processes lead to clear energy savings during refining of pulp and wood fibres and chemical savings in pulp bleaching, thus reducing their environmental impact. Besides, it showed the increased sustainability of the new products, with a lower carbon footprint (e.g. 60% reduction in LPF resins), due to the replacement of petroleum-based components by bio-based ones.
Two patent applications covering new extremozymes have been filed, and a third one related to the new LPF resins is under evaluation. Other results will be directly exploited by partners, through new research contracts or have been published in high impact journals enabling direct knowledge transfer. A Final Workshop was organized to present the main WoodZymes achievements, which are also illustrated in an animated video available at the website.
