Nutritional factors limiting the growth of Lentinula edodes and other white-rot fungi in wood

Wood supplemented with a range of potentially growth-limiting nutrients was inoculated with a variety of lignicolous fungi, including some (Lentinula edodes, Pleurotus sajor-caju, Flammulina velutipes) that form commercially-important mushrooms. Growth was subjectively assessed and also quantified by measuring fluorescein diacetate hydrolysing activity, protein content and chitin content of the cultures. Lignin and dry weight losses were also measured. Most N-containing supplements increased growth while other elements, vitamins or carbohydrates had little effect. Complex N sources (e.g. casein hydrolysate) increased growth more and inhibited lignin degradation less than did simple N-sources (e.g. glutamate). There was considerable inter- and intra-specific variability in the degree to which lignin degradation was inhibited by N. The results indicate that N-availability limits growth rates of fungi on wood while availability of simple carbohydrates, micronutrients or vitamins does not. Lignin degradation is also important for growth, since it may enable fungi to access N-containing components of the wood.