Chitin as an indicator of the biomass of two wood-decay fungi in relation to temperature, incubation time, and media composition

Abstract

Cell wall chitin was determined in the mycelia of the brown rot fungus Neolentinus lepideus (Lentinus lepideus) and an isolate of the soft rot fungus Phialophora sp. to study the correlation to mycelial dry mass. The fungi were incubated as liquid cultures for three incubation periods at three temperatures in six nutrient media with varying levels and combinations of carbon and nitrogen. The glucosamine yield was found to be maximized by hydrolysis at 90°C for 48 h. The chitin content in the studied fungi varied from 8.3 to 39.8 μg.mg-1for N. lepideus and 7.7 to 46 μg.mg-1for the Phialophora isolate. The chitin concentration was remarkably constant, about 10 μg.mg-1, in mycelia growing on the low nitrogen malt extract medium. An experiment with wood blocks indicated that chitin may be a good marker for total fungal biomass production, including living and dead mycelia, in early stages of wood decay (dry weight loss <6%). At higher dry weight losses, the chitin content reaches a plateau or decreases despite continuing degradation as determined by the dry weight loss. The chitin content of visible mycelia growing on wood was determined for both fungi and found to be 19.1 and 12.9 μg.mg-1for N. lepideus and the Phialophora isolate, respectively.Key words: chitin, wood-decay fungi, utility poles, brown rot, soft rot, glucosamine, colorimetry.