Fungal tolerance towards copper-based wood preservatives

Abstract

When wood preservatives against soft rot are used, metal tolerance ability becomes an important fungal peculiarity in the struggle for this ecological niche. Forty two fungal strains belonging to 27 different fungal species from 20 genera were isolated from decaying wood samples. It has been estimated that 81.0% of all strains studied show cellulase (endoglucanase activity) and 57.1% oxidase activity, which are important in assimilating an organic substratum such as wood. Organic acid production was characteristic of only 17.8% of the strains studied, and nearly all of them belonged to the genus Penicillium. Fungal tolerance to copper and resistance to copper-based wood preservatives was estimated. Only three of the strains studied (Amorphotheca resinae 0505, Cladosporium sphaerospermum 9–2, Penicillium funiculosum 0519) grew at 10 mM Cu2+, but their growth was weak. The results showed that susceptibility of the test fungi to wood preservatives as well as their tolerance to copper ions were different and these properties didn’t coincide. The response of strains estimated as the most copper-tolerant to various copper-based preservatives was different: the growth of Amorphotheca resinae 0505 was completely stopped by all the test preservatives, while Cladosporium sphaeropermum 9–2 was completely suppressed only by Impralit-CCO, as was also Penicillium brevicompactum H5–9. Keywords: soft rot fungi, copper tolerance, wood preservatives, cellulase, oxidase, medium acidification