Abstract
Synthetic and heavy metal antifungals are frequently used as wood preservatives. However, they exhibit relatively inert biodegradation and toxic properties when leached; this makes their replacement with environmentally degradable yet functional alternatives a key target in the wood protection industry. In this context, distilled fractions of raw thermomechanical pulp turpentine (TMP-T) from Picea abies were assessed for their wood protecting capabilities against wood-decaying fungi. Antifungal bioactivity of fractions and some of their combinations were screened on agar-plates against the brown-rot fungus Coniophora puteana. Addition of TMP-T fractions showed a significant fungal growth rate reduction, while mixtures indicated the presence of synergistic and antagonistic effects. One fraction, obtained after distilling 1 L TMP-T at 111–177 °C at 0.5 mbar, showed complete growth inhibition of Antrodia sinuosa, Serpula lacrymans, Serpula himantioides and significant inhibition of Antrodia serialis, Antrodia xantha, Gloeophyllum sepiarium, Heterobasidion parviporum at a concentration of 1000 ppm. This fraction was further examined for long- and medium-term effects on wood decay in microcosm soil-jar and field experiment, respectively. The known antifungal compounds benzisothiazolinone, 2-octyl-4-isothiazolin-3-one, 3-iodo-2-propynyl N-butylcarbamate and two commercial wood preservatives were used as reference treatments. Commercial preservatives instilled long-term efficacy against C. puteana wood decay in a soil-jar microcosm experiment, but no noticeable protection with antifungal compounds or the present treatments was found. However, a moderate effect by the TMP-T fraction from the in vitro assay was observed and the TMP-turpentine distillation residue showed a similar fungal inhibition effect to the most potent commercial treatment after 29 months in the field.
Highlights
Wood-decaying fungi are ecologically important for the release of sequestered carbon and nitrogen (Boddy et al 2008), and their ability to degrade wood is of critical importance in nature, they cause detrimental deterioration to wooden structures such as houses, logs and outdoor wood
With increasingly pervasive public environmental concerns, products from nature have in the last decades experienced a renaissance as wood protective measures as well as providing companies with the necessary goodwill incentive to look for more eco-friendly replacements (Sen 2001)
The resulting essential oil is hereafter referred to as thermomechanical pulp turpentine (TMP-T)
Summary
Wood-decaying fungi are ecologically important for the release of sequestered carbon and nitrogen (Boddy et al 2008), and their ability to degrade wood is of critical importance in nature, they cause detrimental deterioration to wooden structures such as houses, logs and outdoor wood. Essential oils from various sources have previously shown inhibitory or biocidal effects on an array of different organisms: parasites (Izumi et al 2012), bacteria (Miladinovic et al 2012), moulds (Akgül and Kivanç 1989), insects (Boulogne et al 2012) and filamentous fungi (Inouye et al 1998). They are generally considered safe for humans and have found long-term use in drug formulations, food preservation and as flavouring agents (Bakkali et al 2008; Smith et al 2005). The aim of the present study was to screen whether antifungal activity of turpentine could be increased by separating its constituents through fractional vacuum distillation
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