Comparison of different methods for collection of volatile chemical markers from fungi

Volatile metabolites from Penicillium vulpinum, cultured on Czapek yeast autolysate agar and broth, were collected by three different methods: (1) diffusive sampling from headspace, (2) purging and trapping of headspace gases, and (3) steam distillation extraction (SDE) of biomass and liquid medium. The qualitative nature and semiquantitative amounts of mainly unsaturated compounds like mono- and sesquiterpenes collected by diffusive sampling were comparable to volatiles collected by purging and trapping. However, the quantitative profiles of volatiles changed towards the lower boiling components with low purge flows, probably due to accumulation of carbon dioxide, demonstrating that the actual purge flow to a great extent determines the quantitative profile of volatile metabolites produced. SDE gave rise to a very different profile compared to the two other methods. None of the major volatiles liberated to the surroundings during growth were dominant in SDE extracts. Instead, lipid degradation products like 1-octene-3-ol and 3-octanone were dominating. The latter method is therefore not recommended as a screening method for volatile chemical markers of active fungal growth.