(604b) Screening Oleaginous Yeast for Lipid Production

Oleaginous yeasts accumulate greater than 20% of their biomass as triacylglycerol in response to nutritional starvation in the presence of excess carbon source. As such, these yeasts have been suggested as a biocatalyst for converting sugars derived from cellulosic feedstocks into biodiesel. Yeast strains belonging to various oleaginous species with a emphasis on Lipomyces and Myxozyma yeasts were selected from the Agricultural Research Service (ARS) Culture Collection (NCAUR, Peoria, IL) and were screened for lipid production. The oleaginous yeast strains were screened in baffled flask cultures using a complex glucose and/or xylose-based medium with a high C:N ratio. Screening was facilitated by adapting a chemical assay that allows for in situ lipid measurement, avoiding the need for extraction. Two strains, from an initial screen of 12, were found to store over 50% of their biomass as lipids. One of these was selected for further study based upon lipid yield and productivity. The strain was able to readily convert xylose and glucose/xylose mixtures simultaneously to lipids at yields near the practical maximum of circa 0.2 g/g sugar. Additional isolates available from the ARS culture collection are now being screened for superior oil-producing ability based upon phylogenetic relationship to this high producing strain.