Eighteen new oleaginous yeast species

Of 1600 known species of yeasts, about 70 are known to be oleaginous, defined as being able to accumulate over 20% intracellular lipids when cultivated under appropriate conditions. These yeasts have value for fundamental studies of lipid synthesis and accumulation, as well as applied studies such as development of improved or new oleochemical production technologies. A survey of yeasts was performed to identify additional oleaginous species, to expand the range of native characteristics such as nutrient utilization, stress tolerance and fatty acid profiles. Yeasts in phylum Basidiomycota were selected from the Phaff Yeast Culture Collection, University of California Davis. Yeasts were selected based on phylogenetic relation to previously known oleaginous species, primarily in taxonomic order Sporidiobolales. Fifty nine strains belonging to 35 species were tested. Yeasts were grown in Medium A, a high carbon, low nitrogen medium known to induce lipid accumulation. Total cell mass and lipid yield were determined gravimetrically. The triacylglycerol fraction and profile was determined as well. Thirty three species accumulated at least 20% lipid by dry weight; of these, 25 species accumulated over 40% lipid. Eighteen of these species were not previously reported to be oleaginous. The most abundant triacylglycerols were TG(16:0/18:1/18:1) and TG(16:0/18:1/18:2), which are ideal for biodiesel production. These results greatly expand the number of known oleaginous yeast species.