How pH and Agitation affect CO2 Production by Yeast

Ellie Hummel, Madysen Jefferies, Garrett Kula, Savannah Lantz, Greg Winkler


Saccharomyces cerevisiae are a viable source for ethanol production and are vital in the productions of many breads and as such, are the subject of many studies on how to minimize costs and maximize their growth. Many factors can affect their growth and the smallest changes can have large impacts on their ethanol and CO2 production. We tested the effect of two factors on their growth, pH and agitation (in the form of a stirring rod in the solution). Our hypothesis was that a lower pH level (around 5) with a constant agitation would allow for the yeast to produce the most CO2. We recorded the CO2 levels from yeast over a 10 minute interval at 3 different pH levels and with the presence of agitation and without any agitation. The agitation did seem to have a positive effect on the CO2 production, though the correlation between pH and CO2 production was a little more ambiguous. Without agitation, the yeast in the acidic conditions produced CO2 at the highest rate, which was what we had hypothesized. However, with agitation, the basic conditions were the most optimal for CO2 production. 

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