A simplified method for extraction of ergosterol from soil

Ergosterol is a sterol common to many fungi and may be useful for estimating fungal biomass in soil. Our objective was to compare three different methods for extracting ergosterol from soil. These included: (i) a published method that involves extraction with methanol, saponification with KOH, and separation with hexane before analysis using high-pressure liquid chromatography (HPLC); (ii) a recently published supercritical fluid extraction (SFE) method; and (iii) a simplified extraction method developed in our laboratory that is similar to method (i) but requires 80 to 90% less reagents. Similar quantities of ergosterol were extracted from both prairie and cropland soil with method (i) and with simplified method (iii). In contrast, the SFE method (ii) did not recover naturally occurring ergosterol from soil. Extraction effciencies of ergosterol standards added to soil were between 75 and 88% for the three procedures, with coefficients of variation of <15% for all methods. Our simplified method substantially reduced cost, extraction time, and chemical waste per sample. Results of this study indicate that the simplified method was the most efficient technique for extraction of ergosterol from soil.