Effect of extractives and thermal modification on antibacterial properties of Scots pine and Norway spruce

Abstract

The effect of thermal modification and extracts of Scots pine sapwood and heartwood, and Norway spruce on the colonisation by the bacterium, Escherichia coli was studied. All wood samples caused more rapid decrease of bacterial numbers compared to glass, which was used as reference material. Pine sapwood caused somewhat faster decrease of bacterial count than the other wood types. On the other hand, both thermal modification and extraction increased the bacterial count on all the samples compared to untreated wood samples. Neither the amount of extractives nor the faster drying of the surface, to which the bacterial inoculum was added, could alone explain this result; rather it is likely that this is due to a combination of both factors.

The influence of wooden interior materials on indoor environment: a review

“…European larch (Larix decidua) wood (Schönwalder et al 2002;Milling et al 2005a;Kavian-Jahromi et al 2015) and bark (Laireiter et al 2013) have exhibited antibacterial characteristics, though variations in results have been reported among different studies. Similarly, Norway spruce (Picea abies) has demonstrated antibacterial effects (Milling et al 2005a;Vainio-Kaila et al 2013;Vainio-Kaila 2017), but the results are more varied, and spruce repeatedly has shown weaker hygienic performance compared with pine (Schönwalder et al 2002;Milling et al 2005a;Vainio-Kaila 2017). Furthermore, antibacterial activity has been found in other species including ash, basswood, beech, birch, butternut, cherry, hard maple and black walnut (Ak et al 1994a, b).…”

“…Milled wood lignin from spruce sawdust exhibited an antibacterial effect on the Gram-positive strain S. aureus (Vainio-Kaila et al 2017a). Furthermore, Vainio-Kaila et al (2013) noticed that altering extractive content through heat treatment or extraction with acetone decreased the antibacterial effect of wooden samples made from pine sapwood and heartwood, and spruce sapwood. Vainio-Kaila et al (2017b) studied the antibacterial effect of volatile organic compounds emitted from milled heartwood and sapwood of Scots pine and Norway spruce.…”

Experimental Parameters Influence the Observed Antimicrobial Response of Oak Wood (Quercus petraea)

“…The lower antimicrobial activity of autoclaved wood samples, as compared to non-sterilized and gamma sterilized wood, shows the loss of some active compounds. As many of the volatile organic compounds (VOCs) are responsible for the antimicrobial action of wood [ 13 ], their loss by high temperature treatment [ 10 , 28 ] might have reduced this ability. This finding is important because the loss of VOCs from wood continues throughout the usage life until reaching a minimum level.…”

“…The antimicrobial characteristics of wood material are attributed to its physical structure and chemical composition, which can create unsuitable survival conditions for different microbes [ 9 ]. As this physiochemical profile differs between wood species, the antimicrobial activity also varies accordingly [ 10 , 11 ]. For example, some wood extractives contain active antimicrobial compounds, such as tannins and phenolics; however, their presence and distribution vary in different wood species, and even in different parts of the same tree [ 1 , 12 ].…”

“…Antimicrobial properties of wood are generally tested via extractive based methods, i.e., various solvents are used to remove compounds naturally found in wood [ 1 , 2 , 10 , 13 ]. The extracted compounds can be used to obtain a quantitative measure of antimicrobial action [ 14 ].…”