Detection of metal-chelating compounds from wood-rotting fungi Trametes versicolor and Wolfiporia cocos

For many years, the wood decay process by fungi was associated almost exclu sively with production of lignocellulolytic enzymes. However, recent studie s by electron microscopy have shown that fungal enzymes are too large to pe netrate into the cell wall at an early stage of decay. Thus, the hypothesis that low molecular mass agents may initiate the breakdown of both cellulos e and lignin was proposed. The purpose of this work was to detect low molec ular mass compounds, with metal-chelating capability, from liquid cultures of two wood-rot fungi. The brown-rot fungus Wolfiporia cocos produced the h ighest chrome azurol S (CAS) reaction, simultaneously reducing the pH of th e malt extract medium. In contrast, the white-rot fungus Trametes versicolo r did not react with CAS and the pH remained approximately constant during the culture period. The presence of hydroxamate derivatives and oxalic acid was detected in extracts of low molecular mass of both fungi. Moreover, in W. cocos extracts, catecholate derivatives were also detected. Accumulatio n of oxalic acid was greater in W. cocos than in T. versicolor at the end o f the culture period, and this might be responsible for the strong response from W. cocos in the CAS reaction.