The influence of pH on pigment formation by lignicolous fungi

Wood-decay patterns are strongly influenced by the conditions of the wood substrate, and the pH of the substrate is one of the most important factors. As a reaction to a stressed environment, some lignicolous fungi respond with pigment formation that helps to isolate and protect their mycelia; other fungi, with high specificity, produce pigmentation regardless of the changes in the conditions in which the fungus grows. These changes result in only minor variation in the color intensity of the pigment. The occasional dark-colored reaction pigment, also known as melanin, is the most common pigment formed by wood-decay fungi. To investigate pigment formation under the influence of pH variation, sugar maple and beech samples adjusted with buffer solutions to different pH values were inoculated with various basidiomycetes and ascomycetes fungi, known to produce pigmentation. Based on the range and increments of the pH treatments tested on the wood substrate, maximum pigmentation and minimum mass loss occur at adjacent values of pH treatments for all wood fungus combinations, and never coincide. Maximum pigment production occurred at treatment with pH 4.5 for beech and sugar maple inoculated with Trametes versicolor, while Xylaria polymorpha produced external pigmentation in beech treated with buffer at pH 5 and sugar maple at pH 4.5. Fungi tested in agar substrate produced maximum pigmentation at the pH range 4-5.5, except for Scytallidium cuboideum, which produce maximum intensity of red pigment at pH 6 and blue pigment at pH 8. (C) 2013 Elsevier Ltd. All rights reserved.