Effects of biocides on the extracellular mucilaginous material (ECMM) produced by two wood rotting basidiomycetes
D Vesentini, D J Dickinson, R J Murphy
Growth and production of extracellular mucilaginous material (ECMM) by the brown-rot fungus Gloeophyllum trabeum (FPRL 108 N) and the white-rot fungus Coriolus versicolor (CTB 863 A) was assessed in liquid culture, supplemented with the biocides CuSO4 and cyproconazole.
The production of biomass in G. trabeum was significantly influenced by the concentration of CuSO4 in the medium. When CuSO4 was added at 1.0 mmols l-1, biomass was reduced by approximately 35%. At this concentration, the production of ECMM, both absolute and relative to biomass, was increased. Cyproconazole had a similar effect to that observed for CuSO4, although much lower concentrations of the biocide were required to achieve a similar response. Addition of 0.1 mmols l-1 of cyproconazole to the growth medium caused a decrease of approximately 35% in the amount of biomass produced and a 200% increase in the proportional amount of ECMM produced by the fungus.
A similar behaviour was also confirmed for C. versicolor . In this case, higher concentrations of CuSO4 were required in order to achieve the same levels of inhibition observed for G. trabeum. Cyproconazole-supplemented cultures also behaved similarly to G. trabeum. A concentration of cyproconazole of 0.1mmols l-1 caused a reduction of 50% in biomass and a 100% increase in the proportional amount of ECMM produced by this fungus.
The presence of biocide also led to qualitative changes in the composition of ECMM. Galactose, xylose and glucose were the main components of the polysaccharide fractions of the ECMM produced by the two species growing on control media. As biocides were introduced, the proportion of galactose in the ECMM increased. This was always associated with a decrease in the proportion of glucose for G. trabeum and with a decrease in the proportion of xylose in the ECMM produced by C. versicolor.
The results are discussed with regard to the possible role(s) of ECMM in the decay process and its interaction with preservative treatments.