ERGOSTEROL AS AN INDICATOR OF MOLD GROWTH ON WOOD IN RELATION TO CULTURE AGE, HUMIDITY STRESS AND NUTRIENT LEVEL

Changes in ergosterol content in cultures of Penicillium brevicompactu m and Aspergillus versicolor on wood with time, changes in humidity or addition of glucose solution to wood were studied with HPLC. Lowering of the humidity level caused a very large decline in ergosterol conte nt of cultures of P. brevicompactum on wood over a 10 day period, alth ough small amounts remained after this time. After an initial increase , up to an inoculation time of of 45 days, reductions were also observ ed in control samples maintained at 100% RH, but these were smaller. T he amount of ergosterol decreased to very low levels in wood impregnat ed with low levels of glucose during a 93 day incubation period. Ergos terol concentration in hyphae produced in surface liquid cultures was shown to be higher in mycelia growing on media enriched with nitrogen or with more available nutrients. The concentration of ergosterol in t he mycelia of P. brevicompactum in surface liquid cultures varied by a factor of 5 from 2 to 10 mg g(-1). The results clearly show that ergo sterol present in solid materials is mainly related to active biomass. With certain prerequisites, ergosterol determinations could also be u sed for total fungal biomass estimations on wood.