That’s Acidic: Testing How Different pH Levels Affect the CO2 Production of Saccharomyces cerevisiae

Abstract

Baker’s yeast is an important ingredient in bakery items, brewing, and industrial ethanol. Yeast has also been found to be useful in the production of biofuels, which has caused increased interest in maximizing the CO₂ production of yeast. The CO₂ production of yeast is affected by temperature, agitation, osmotic pressure, as well as other factors, such as pH. The aim of our experiment was to test how differences in pH levels affected the CO₂ production of Saccharomyces cerevisiae. We used 0.5 M sodium phosphate with different pH of 7 as our control, as well as pH of 5 and 6. The pH of the solution after adding the pH buffers was determined using pH strips and comparing the color to a pH indicator chart. This is a measure of the rate of cellular respiration by the yeast. Our hypothesis is that a pH level of 7 will cause an increase in CO₂ production due to the yeast cells’ proteins favorability of neutral conditions. We found that as the pH decreased, the CO₂ production rate also decreased, so our hypothesis was supported.