Does pH affect yeasts’ respiration?
Abstract
We studied the effects of pH on CO2 output as a factor of growth rate. Acme Brewing and Baking Company is conducting several experiments to determine the ideal conditions for fermentation and bread production. As part of their research team we chose to study pH effecting growth. We predicted that the yeast would reproduce faster in acidic environments, but the data we found did not support this prediction.
Introduction
Acme Brewing and Baking Company has hired us to determine the optimum growing conditions for their yeast production (French, 2015). Some research that led us to our hypothesis was the work of Nicolay (1987) who determined that yeasts are able to live in extreme environments because …show more content…
Our dependent variable is the growth of the yeast. We ran several trials to determine the effects of pH on the growth rate of yeast. For the baking soda trials, we first weighed the sugar (sucrose) to .75g and added it to the beaker. Then we added 37.5 mL of water. Next we added 200μL of sodium phosphate (NaPO3-) and 37.5mL of 10% weight by volume liquid baking soda. We measured the pH. Then we added .25g of dry yeast. Next we placed a CO2 probe in the beaker and measured the CO2 output over a period of 30 minutes. We are measuring the CO2 output as a factor of the growth rate. For the water (neutral) trial, we weighed out .75g of sucrose and put in the beaker, then added 75 mL of water and 200µL of NaPO3- and .25g of yeast and stirred. The water was not distilled water it was tap water. This gave us a pH of 7.8 instead of exactly 7, but still fairly neutral. For the vinegar trial, we weighed the same amount (.75g) of sucrose and 38.5mL of water to a beaker. Then we added 200µL of NaPO3- and 36.5mL of vinegar. Then add .25g of yeast. We measured the pH. Then we repeated the same procedure for another …show more content…
Upon further study we realized that the baking soda submerged in water was producing CO2 because the formula for baking soda is H2CO3 and when submerged in water it reacts with H2O to form CO2. This resulted in the baking soda trial producing significantly more CO2 than we hypothesized. To be sure that this was the reason the baking soda produced more CO2 we had to put all of the trials through a spectrometer to determine the optical density. The spectrometer measures how much light gets through the solution, so the less light that passes through means the higher concentration of yeast in the solution. Our findings from the spectrometer showed that the baking soda actually did produce more yeast than the vinegar and water. This does not support our hypothesis because we predicted that the vinegar solution would produce more yeast because it is acidic. In conclusion, we found that yeast grows better in basic environments so Acme should use basic solutions to maximize their efficiency. However, Adoki stated that yeast grows best in an acidic pH level by testing oranges, plantains, and bananas (2008). Future researchers could follow up on our experiment by exchanging another basic solution such as bleach instead of baking soda, so that they could more accurately measure the yeast growth and CO2
Abstract
We studied the effects of pH on CO2 output as a factor of growth rate. Acme Brewing and Baking Company is conducting several experiments to determine the ideal conditions for fermentation and bread production. As part of their research team we chose to study pH effecting growth. We predicted that the yeast would reproduce faster in acidic environments, but the data we found did not support this prediction.
Introduction
Acme Brewing and Baking Company has hired us to determine the optimum growing conditions for their yeast production (French, 2015). Some research that led us to our hypothesis was the work of Nicolay (1987) who determined that yeasts are able to live in extreme environments because …show more content…
Our dependent variable is the growth of the yeast. We ran several trials to determine the effects of pH on the growth rate of yeast. For the baking soda trials, we first weighed the sugar (sucrose) to .75g and added it to the beaker. Then we added 37.5 mL of water. Next we added 200μL of sodium phosphate (NaPO3-) and 37.5mL of 10% weight by volume liquid baking soda. We measured the pH. Then we added .25g of dry yeast. Next we placed a CO2 probe in the beaker and measured the CO2 output over a period of 30 minutes. We are measuring the CO2 output as a factor of the growth rate. For the water (neutral) trial, we weighed out .75g of sucrose and put in the beaker, then added 75 mL of water and 200µL of NaPO3- and .25g of yeast and stirred. The water was not distilled water it was tap water. This gave us a pH of 7.8 instead of exactly 7, but still fairly neutral. For the vinegar trial, we weighed the same amount (.75g) of sucrose and 38.5mL of water to a beaker. Then we added 200µL of NaPO3- and 36.5mL of vinegar. Then add .25g of yeast. We measured the pH. Then we repeated the same procedure for another …show more content…
Upon further study we realized that the baking soda submerged in water was producing CO2 because the formula for baking soda is H2CO3 and when submerged in water it reacts with H2O to form CO2. This resulted in the baking soda trial producing significantly more CO2 than we hypothesized. To be sure that this was the reason the baking soda produced more CO2 we had to put all of the trials through a spectrometer to determine the optical density. The spectrometer measures how much light gets through the solution, so the less light that passes through means the higher concentration of yeast in the solution. Our findings from the spectrometer showed that the baking soda actually did produce more yeast than the vinegar and water. This does not support our hypothesis because we predicted that the vinegar solution would produce more yeast because it is acidic. In conclusion, we found that yeast grows better in basic environments so Acme should use basic solutions to maximize their efficiency. However, Adoki stated that yeast grows best in an acidic pH level by testing oranges, plantains, and bananas (2008). Future researchers could follow up on our experiment by exchanging another basic solution such as bleach instead of baking soda, so that they could more accurately measure the yeast growth and CO2