Enzymatic modification of lignin

VTT - Technical Research Centre of FinlandInstitute:

VTT – Technical Research Centre of Finland
Dpt. Processing of Biomass Components


P.O. Box 1000
FIN-02044 VTT

Project leader:

Dr. Tarja Tamminen (tarja.tamminen(at)vtt.fi)


VTT will develop methods to modify lignin, aiming at reducing its odour and improving its ability to bind with the reinforcement fibres in composites. The methods tested will be based on treatment with laccases in the presence or absence of added mediator.

Different laccases will be tested, differing in their redox potential and pH and temperature optima:

  • Trametes hirsuta and Melanocarpus albomyces laccases produced at VTT
  • Laccases provided by other project partners
  • Laccases provided by industrial partner ROAL

The extent of oxidation under various laccase treatment conditions will be followed based on oxygen consumption.

The laccase treatments as such are expected to induce phenoxyl radicals to lignin, which react further mainly by coupling reactions. In the presence of mediators, the reaction may be directed towards degradation rather than polymerisation. Known mediators, such as hydroxybenzotriazol (HBT) and N-hydroxyacetanilide (NHA) will be tested.

The effects of the enzymatic treatments on lignin will be followed by chemical analyses:

  • Changes in molar mass distribution by size exclusion chromatography
  • Small to medium sized degradation products by MALDI-TOF/MS
  • Changes in functional groups (aliphatic hydroxyl groups, different types of phenolic hydroxyl groups, carboxylic acids) by 31P NMR after derivatisation
  • Thermal and physical properties by DSC analyses

The mechanisms and factors affecting the oxidative enzyme catalyzed linking of lignin to fibre material will be elucidated, aiming at defining feasible modification conditions for the application of lignin as composite binder.

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