Enzymatic functionalization – The environmentally friendly way to treat wood

Exterior wall of a wooden hut. The wooden boards are weathered.

The conventional treatment of wood in order to increase its hydrophobicity implies disadvantages that could be avoided when using environmentally-friendly processes. New methods that are increasingly being investigated use enzymes, like laccases, lipases and peroxidases in order to graft various molecules onto the wood surface to alter its properties.

Increased hydrophobicity of wood surfaces is desired as it improves strength, reduces the biodeterioration and sometimes it is simply to improve aesthetic properties of the material. A lot of chemical, physical and physicochemical methods are known, that have considerable disadvantages, like reducing mechanical strength, release of the impregnating agent into the environment or energy demanding.

Enzymatic grafting provides an environmentally friendly alternative to treat wood without any of the above mentioned drawbacks. One outstanding enzyme that is used for this purpose derives from the group of oxidoreductases. This group of enzymes was first isolated from the japanes lacquer tree, this is also where the name „laccase“ derives from. These enzymes have been used in different studies to mediate the grafting of fluorophenols, long chain alkylamines, reactive phenolic amines and wood preservatives onto wood surfaces to alter their functionality.

acib researchers followed different strategies to enzymatically treat lignocellulosic material. On the one hand, functional phenolic molecules and dimer fatty amines were grafted onto flax and coconut fibers on the other hand, fatty acids were grafted onto wood veneers. The latter-mentioned study included a mechanistic investigation of the coupling reaction using fatty acids and model molecules representing hardwood lignin substructures. It could be shown that enzymatic grafting reactions result in stable covalent bondings, that provide a longlasting altered functionality to the material.

This work is based on:  
Greimel K, Kudanga T, Nousiainen P, Sipilä J, Herrero Acero E, Nyanhongo G, Guebitz G. (2017) Two distinct enzymatic approaches for coupling fatty acids onto lignocellulosic materials. Process Biochem 59:111–115. doi:10.1016  
Herrero Acero E, Kudanga T, Ortner A, Kaluzna I, de Wildeman S, Nyanhongo G S, Guebitz G. (2014) Laccase functionalization of flax and coconut fibers. Polymers (6) 1676-1684.  
Picture credits: pixabay