Application of fatty acid profiles in the identification of yeasts.

In order to develop a rapid yeast identification technique using fatty acid profiles, an extensive survey has been conducted in our laboratory on the long-chain fatty acid composition (CLFAC) of yeasts representing the endomycetous and basidiomycetous yeast domain. It was accomplished by cultivating the yeast strains under standardized conditions in a synthetic liquid medium. When stationary phase was reached the cells of each culture were freeze-dried and the CLFAC was examined by gas chromatography. It was found that the fatty acid profile obtained for each strain was reproducible. However, as work progressed, it became clear that variation exists within species and that the relative percentages of some strains from different species may overlap. Identification of species could therefore not be achieved in all attempts, even when the resolution of the fatty acid analyses was enhanced by using capillary columns, useful for the detection of minor fatty acids. When used in isolation, CLFAC analyses is therefore not a generally applicable identification technique for yeast species. However, the technique was found to be a valuable chemotaxanomical tool to distinguish between strains of certain species, species of certain genera and species from particular environments. The technique currently finds application in the South African food and beverage industry as a quick, cheap and easy way to distinguish between strains of Saccharomyces cerevisiae. It is also used by an industry which produces bioprotein from Geotrichum candidum, to determine fungal contaminants in a quality control process.