Essential oils from Thymus spp. as natural biocide against common brown- and white-rot fungi in degradation of wood products: antifungal activity evaluation by in vitro and FTIR analysis

Abstract

Use of wood products in bio-building is increasing because of the raw material’s sustainability and renewability. Degradation of wood by fungi is one of the most significant threats in the use of wooden structures. In the past, degradation was prevented by the application of wood preservatives or the use of durable tropical species. Therefore, wood preservation by fossil-based compounds and heavy metals is one of the major issues. This study evaluated the antifungal activity of four essential oils of thyme species (Thymus capitatus, Coridothymus capitatus, T. vulgaris, and T. vulgaris Demeter, collected from organic and biodynamic farms, respectively) against two white-rot fungi (Trametes versicolor and Pleurotus ostreatus) and two brown-rot fungi (Poria monticola and Gloeophyllum trabeum). The thyme varieties’ essential oils differed in their chemical composition, with either carvacrol, thymol or p-cymene as major components. All four essential oils showed good antifungal activities, in which T. capitatus was the most toxic when applied against P. monticola (MIC of 0.05) and the most efficient inhibiting the growth of the other fungal strains. Fourier transform infrared (FTIR) spectroscopy was applied to investigate fungal cell wall structure under control and stress conditions. The results are a further step towards more eco-friendly solutions for preserving less durable wood products more frequently used in bio-building.