Investigating the Impact of Glucose and Fructose as Carbon Sources on Xylitol-Induced Inhibition of Yeast Fermentation Rate

The process of yeast fermentation plays a huge role in many of the aspects of our world today, but most recently in the way it has more been found to have a profoundly positive impact on wastewater remediation, as well as in biofuel production. The process requires the use of carbon sources, most commonly glucose, fructose, or sucrose, and oftentimes occurs most effectively with the use of glucose. As helpful as this process is, there are quite a few factors that seem to interfere with it in the environments of wastewater treatment plants and biofuel production factors, namely the presence of multiple carbon sources, and xylitol. Xylitol is a known competitive inhibitor in the yeast fermentation process. This paper therefore examined the use of glucose and fructose as a carbon source in yeast fermentation, investigating whether either of these sources slow or inhibit the process when xylitol is present. Yeast fermentation rate was measured through taking the height and circumference of balloons secured over each technical replicate periodically. This approach allowed for the rate to be measured in terms of carbon dioxide production by the yeast as it fermented. Balloon circumference and height were analyzed separately using linear mixed-effects models that accounted for repeated measurements from each tube. Circumference showed a significant carbon source × xylitol concentration × time interaction, whereas height showed a significant carbon source × time interaction but no significant three-way interaction. These results overall supported there being an increasingly negative impact on yeast fermentation rate when glucose and fructose were used as a carbon source while xylitol concentration was increased incrementally. The results provide valuable insight into what factors should be more heavily considered in future wastewater treatment and biofuel production plans, in order to ensure their highest efficiency.