Evaluation of a simple, non-alkaline extraction protocol to quantify soil ergosterol

SummaryQuantification of soil ergosterol is increasingly used as an estimate for soil fungal biomass. Several methods for extraction of ergosterol from soil have been published, perhaps the simplest being that described by Gong, P., Guan, X., Witter, E. [2001. A rapid method to extract ergosterol from soil by physical disruption. Appl. Soil Ecol. 17, 285–289]. This method only involves a mechanical disruption of soil mycelium by glass beads in methanol and direct HPLC analysis of the ergosterol in the filtered methanol extract. However, it has not been compared with more complex extractions that include a saponification step to liberate both free and esterified ergosterol. In this study, we have compared the Gong method with a method involving saponification for a number of sandy and clayey soils as well as for organic layers of forests. In addition, we compared both methods with respect to recovery of added ergosterol and fungal hyphae. The Gong method appeared to be as good as the method including saponification, provided that the amount of soil to be extracted was lowered with respect to the original protocol when analysing soils with an organic matter content >5%.