Introduction: Fermentation is a metabolic process that occurs in the absence of oxygen molecules, also known as an anabolic reaction. It is a process of glycolysis in which sugar molecules are used to create ATP. Fermentation has many forms, the two best known examples are lactic acid and alcoholic fermentation (Cressy). Lactic acid fermentation is used in many areas, from food production such as bacteria to its use by fatigued muscles in complex organisms (Cressy). When you experiment with organisms like yeast, as was done in this experiment, you follow the metabolic pathway of alcoholic fermentation (Sadava). Where sugar molecules are broken down and become ethanol (Sadava). But the end product of fermentation is the production of ATP, which allows a small amount of energy to be produced to maintain metabolic functions while the system in question replenishes its oxygen. Yeast cannot ferment without a substrate, the best known substrate is glucose. There are many ways to observe fermentation. Alcohol, ATP and CO2 are all measurable products of fermentation. The one most easily measurable by the common eye is the production of gas. Showing the amount of CO2 produced can be a relationship between fermentation speed and time. There are factors that can affect the rate of fermentation, such as temperature, substrate concentration and pH level. This experiment focuses on how much fermentation can occur under certain conditions. The pH levels will change the rate at which the yeast ferments and produces CO2. Every biological reaction occurs at some optimal level within ranges of pH, temperature and light, whatever the factors determining that reaction. So we need to test all the levels we can think of to find the optimal range and see how much they differ... middle of paper... H. O'neil. Online Lab Tutor. Np: np, nd Print. Galafassi S, Merico A, Compagno C, et al. Dekkera/Brettanomyces yeasts for the production of ethanol from renewable sources under limited oxygen and low pH conditions. Journal of Industrial Microbiology & Biotechnology [serial online]. August 2011;38(8):1079-1088. Available from: Academic Research Completed, Ipswich, MA. Accessed 23 February 2014.Huang H, Guo X, Li D, Liu M, Wu J, Ren H. Identification of crucial yeast inhibitors in bioethanol and improved fermentation at high pH and high total solids. Bioresource technology [online serial]. August 15, 2011;102(16):7486-7493. Available from: Academic Research Completed, Ipswich, MA. Accessed February 23, 2014. Sadava, David E., David M. Hillis, H. Craig Heller, and May R. Berenbaum. Life: the science of biology. 10th ed. Sunderland, MA: Sinauer Associates, 2014. Web.