(23b) Exploring Mechanisms for Xylose Transport in the Oleaginous Yeast, Yarrowia Lipolytica

The biological production of fuels and chemicals by microorganisms has garnered interest as an alternative to petroleum-derived products. Using lignocellulosic feedstocks enables renewable production without competing for food supplies. However, many industrial microorganisms do not efficiently metabolize xylose and other pentose sugars resulting from lignocellulose hydrolysis. As a result, much effort has focused on engineering microorganisms for efficient xylose utilization. The oleaginous yeast, Yarrowia lipolytica, is capable of accumulating lipids >90% of cell biomass, making it ideal for production of fatty acid-based products. While there are conflicting reports in the literature, our experiments show that Y. lipolytica is unable to utilize xylose as a sole carbon source. It remains to be understood whether the significant bottleneck in the process lies in the transport of xylose or its metabolism. Here, we explore sugar transporter homologs in Y. lipolytica that share strong sequence similarity to well-characterized xylose transporters in Scheffersomyces stipitis and Candida intermedia. We used confocal microscopy to determine whether the identified homologs localize to membrane and determine preferential sugar uptake through these transporters via a series of knockout studies and substrate assays. Furthermore, recombinant expression studies with xylose transporters from S. stipitis and C. intermedia will be done, engineering the Y. lipolytica to have a preferential uptake towards xylose. The work presented here complements the xylose metabolism work currently performed by our lab and will advance the current limited knowledge of Y. lipolytica 5-carbon sugar transport and metabolism.