Influence of a nitrogen supplement on the growth of wood decay fungi and decay of wood

Bioremediation processes require cheap and effective nutrient sources which contain significant amounts of nitrogen, e.g. corn steep liquor (CSL). In order to elucidate fungal copper tolerance in a nitrogen-rich environment, experiments were performed on a nutrient medium and with wood. CSL was added to nutrient medium containing different copper concentrations and to Norway spruce (Picea abies) wood specimens impregnated with a commercial copper-based preservative (CCB). Sterilized CCB-impregnated and control CSL-supplemented specimens were exposed to copper-tolerant (Antrodia vaillantii, Leucogyrophana pinastri) and copper-sensitive (Postia placenta, Gloeophyllum trabeum, Trametes versicolor and Hypoxylon fragiforme) fungal species according to the mini-block procedure. Additionally, nutrient media containing CSL and copper(II) sulphate of different concentrations were inoculated with the same fungi and the growth of the fungal hyphae was visually estimated. The results of both experiments showed that CSL increases the ability of the copper-sensitive brown- and white-rot fungi to grow on copper-containing substrates. CSL inhibited growth of the copper-tolerant fungi on nutrient medium containing copper and decreased decay of CCB-preserved wood. It is believed that the reason for changed copper tolerance originates in copper-tolerant fungi producing less oxalic acid in the presence of high concentrations of nitrogen in the growth environment.