Tuesday, April 30, 2013
Exhibit Hall
Oleaginous (high lipid) yeasts may be a new source of oil for biodiesel and other oleochemicals. While several oleaginous yeast species are known, most of the known yeast species have not been analyzed to determine their lipid content. We are working to expand the known panel of oleaginous yeast species to allow selection of yeast strains with appropriate growth characteristics such as nutrient utilization and toxin tolerance, for conversion of various types of biomass to lipids. We isolated novel yeast strains from the rain forest in Indonesia. We selected 70 yeast strains from this study and additional archived strains from the Phaff Yeast Culture Collection for analysis, based on phylogenetic similarity to known oleaginous species, buoyancy observations, and source habitat. We found that more than 60% of these selected yeasts were able to accumulate intracellular lipids greater than 20% of their cellular weight as determined by a gravimetric assay. Several species accumulated >50% lipids by dry weight. Fatty acids were identified and quantified by GC-FID. Yeasts grown in a nitrogen-limiting medium generally showed higher total intracellular lipid content than when nitrogen was not limiting. The most prevalent fatty acids were oleic acid (18:1ω9), palmitic acid (16:0), linoleic acid (18:2ω6), and stearic acid (18:0). Synthesis of linoleic acid (18:2ω6) was accelerated in many yeasts in media without nitrogen source. The composition of these yeast oils is similar to plant and microalgae oils currently used for biodiesel, with high lipid accumulation observed within five days of growth in laboratory media.