We have been attempting to engineer a yeast strain capable of efficiently utilizing full sugars for the economical production of biofuels. Our efforts focus on Saccharomyces cerevisiae, the pre-eminent microorganism for industrial production of ethanol. Compared to other potential biofuel-production hosts such as E. coli and Z. mobilis, S. cerevisiae has several advantages. For example, S. cerevisiae is robust, tolerant to relatively high concentrations of product and inhibitors present in lignocellulosic hydrolysates, and viable at lower pH. In addition, yeast has a short doubling time, its genetics and physiology are well-studied, and many genetic engineering tools are available. In this talk, I will discuss our recent progress on: (1) construction of pentose utilization pathways in S. cerevisiae, (2) discovery and characterization pentose specific transporters; and (3) use of genome-scale modeling coupled with metabolic engineering and synthetic biology approaches to optimize sugar utilization pathways for ethanol production.