Effect Of Sucrose Concentration On Yeast Fermentation

In this lab, yeast undergoes alcoholic fermentation with nine different sugars—glucose, sucrose, truvia, lactose, saccharin, starch, maltose, fructose, and sucralose. The fermentation rates were determined by observing the rate at which carbon dioxide is produced in the flask; since the gas can not be seen in this case, the water displacement within a pipet that is connected to the flask, would illustrate the production of CO2 gas. According to our data, sucrose fermented the fastest and sugars like lactose, truvia, and starch did not ferment in the seven to nine minute time frame. These results support the idea that yeast ferments at different rates with broader implications for how the human digestive system works.

Introduction

Saccharomyces

This poses the question: if most sugars of different chemical structures can ferment, why is it that certain sugars like lactose and starch cannot be fermented? One way to approach this question is through the investigation of enzymes. In many cases such as lactose and starch, sugars lack enzymes that are necessary in the process of fermentation [2]. For instance, lactose sugars are not able to ferment because they lack the enzyme lactase which is needed to hydrolyze lactose—a disaccharide composed of galactose and glucose [1]. When starch, a polysaccharide sugar, can be fermented by an organism, it is likely that other starches can also be decomposed by the same enzyme within the organism [3]. However, S. cerevisiae is unable to ferment the starches on its own and requires the enzyme Alpha-amylase to catalyze the hydrolysis process that decomposes starch into monosaccharides [5]. Furthermore, research shows that sugars like sucrose are able to be fermented by the yeast and water solution due to the invertase enzyme that is secreted from the yeast [4]. This enzyme digests the sucrose into glucose and fructose which are monosaccharide sugars that cells can import