Evaluation of methods to extract ergosterol for quantitation of soil fungal biomass

Two methods were evaluated to extract ergosterol for quantitation of fungal biomass in Marshan, Zurich, and Batavia soils. Yields of ergosterol from hyphae and from fungal-colonized soil were greater when fungal tissue was extracted with an alkaline solvent mixture than when base was added to neutral extracts following removal of solids. A lyophilization treatment prior to extraction increased yields from Marshan but not from Zurich and Batavia soils. Losses of ergosterol during lyophilization were prevented by a rapid freezing treatment before lyophilization of soil samples. Recoveries from soil fortified with pure ergosterol did not accutately model recoveries from fungal tissue in these substrates. Thus, determinations of extraction efficiencies should be based upon recoveries from fungal tissue added to soils. Ergosterol was quantitatively recovered from Marshan and Zurich soils fortified with fungal tissue; however, only ca 66% was recovered from Batavia soil, a subsoil with a high clay content. The limit of detection of Phanerochaete chrysosporium from the three soils ranged from 8 to 15 μg biomass g soil −1.