(459c) Rewiring Native Metabolism of Yarrowia Lipolytica for Enhanced Assimilation of Complex Biomass-Derived Sugars and High-Yield Production of Organic Acids

While the model oleaginous yeast Yarrowia lipolytica is well known for decades to grow mainly on C6 sugars, its native metabolic capability to assimilate xylose and cellobiose, dominant sugars derived from lignocellulosic biomass, is poorly understood. In this study, we elucidated and activated native xylose and cellobiose pathways of Y. lipolytica through comprehensive metabolic and transcriptomic analyses. We identified 7 glucose-specific transporters, 16 xylose-specific transporters, and 4 cellobiose-specific transporters that were transcriptionally upregulated for growth on respective single sugars. While Y. lipolytica is capable of using xylose as a carbon source, xylitol dehydrogenase (XYL2) is the key bottleneck of xylose assimilation. Y. lipolytica has a set of 5 extracellular and 6 intracellular beta-glucosidases (BGLs) to assimilate cellobiose via both extra- and intra-cellular mechanisms, but the latter being dominant for growth on cellobiose as a sole carbon source. By tuning the expression of native metabolic enzymes and transporter genes, we engineered a Y. lipolytica mutant with enhanced assimilation of xylose and cellobiose as well as their mixtures with glucose. Further, we demonstrated the performance of Y. lipolytica mutant for high-yield production of high-value organic acids (e.g., alpha-ketoglutaric acid) using ionic liquid-pretreated lignocellulosic biomass in a simultaneous saccharification and fermentation process.