Developing an unstructured model to investigate the effect of ethanol on product yields for glucose and xylose cofermentation in Saccharomyces cerevisiae 424A (LNH-ST)

Production of bio-ethanol from lignocellulose requires the efficient fermentation of glucose and xylose, even in the presence of inhibitors. The desired product, ethanol itself, will inhibit the fermentation. A further understanding of how ethanol affects the organism is critical to overcoming its inhibition. This thesis evaluated the effect of ethanol on the cofermentation of glucose and xylose in two different cases. The first case had an unstructured model created for Saccharomyces cerevisiae 424A (LNH-ST), a genetically modified strain of yeast capable of cofermenting glucose and xylose. The differential equations were based around sugar consumption, and the product yields were investigated to see how each were affected by ethanol. Results show that ethanol has a significant impact on all xylose product yields except for cell growth and xylitol. The second case compared the specific xylose consumption rates at increasing ethanol concentrations of S. cerevisiae 424A (LNH-ST) and two adapted strains. The ethanol adapted strain performed better, and it produced ethanol at a higher yield.