A. Generate a fermentation profile for each of the organisms you tested.

Glucose fermentation shows the ability of a bacterium to ferment carbohydrate as well as its ability to convert end products (pyruvic acid) into gaseous byproducts (Levinson, 2014). During this experiment 2 of the Staphylococcus epdidermidis tubes turned yellow. It was difficult to tell if there was an air bubble in any of the tubes that turned yellow, so I may be wrong on some of the fermentation profiles. The S. cerevisiae showed to be yellow on all 3 sugars and I think I observed air bubble in the tube with glucose. Fermentation profile for S. epdidermidis Fermentation profile for S. cerevisiae
• Glucose A • Glucose AG
• Fructose A • Fructose A
• Mannitol- • Mannitol A
B. Explain why it is important not to incubate the fermentation tubes beyond 24 hours.
After 24 hours, the sugar tests have higher risk of a color change because when the microbe runs out of sugar they will use protein or other nutrients as a food source. If it uses protein, they produce alkaline by-products, and the medium can change color because of the pH indicator added to detect acid production causing an inaccurate result.
C. Explain why phenol red is added to the fermentation tubes.

Durham tubes collect CO2 gas produced from fermentation process. Phenol red is added to the tube because it’s a pH indicator, thus is also added to a medium in a fermentation series. Phenol red will turn yellow below ph 6.8 and will turn a darker pinkish-red above pH 7.4. If the organism is able to utilize the carbohydrate, an acid by-product is created, which turns the media yellow. If the organism is unable to utilize the carbohydrate but does use the peptone, the by-product is ammonia, which raises the pH of the media and turns it pinkish-red. It tests an organism's ability to