Enabling xylose metabolism from A cryptic pathway in 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 neutral lipids and fatty acid-based oleochemicals. While there are conflicting reports in the literature, our experiments initially showed that Y. lipolytica is unable to utilize xylose as a sole carbon source. However, we systematically investigated the xylose pathway in Y. lipolytica by testing the functionality of putative xylose metabolism genes and identified genes that when overexpressed lead to robust xylose metabolism. We confirmed the function of these genes through enzymatic assay, E. coli growth complementation, knockout, and overexpression in Y. lipolytica. We further improved the xylose metabolizing capabilities of Y. lipolytica by overexpression of endogenous and heterologous sugar transporters. Finally, we will describe our most recent findings using transcriptomics and metabolomics to understand the basis of this cryptic metabolic pathway, its regulation, and develop strategies to improve lipid yields from xylose.