Research combination of biological and nonbiological factors leading to

Research Question: What are the rates of CO2  production when fermentation of Saccharomyces pastorianus  is made to proceed in the presence of  temperatures between 5 to 20 degrees celsius in a test tube of  18×150  diameter in a room with no temperature alterations?


Background Information:

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Yeast cells like all other living things need energy to maintain their structures, reproduce and grow. This energy is obtained by breaking down biomolecules using cellular respiration. When oxygen is present the yeast will obtain his energy by breaking down sugars into CO2 and water.When there is no Oxygen yeast will use aerobic respiration, known as alcohol fermentation where the yeast partially break. Saccharomyces pastorianus which comes from the same species as Saccharomyces cerevisiae is a combination of biological and nonbiological factors leading to this interspecific hybrid yeast species becoming one of the world’s most important industrial organisms. This yeast is used in the production of lager-style beers, the fermentation of which requires very low temperatures compared to other industrial fermentation processes. It has strong fermentative ability thanks to the mixture and hybridization of it and it is normally used to produce lager beer.


In the experiment  we will see that when yeast ferments the sugars anaerobically, CO2 production will cause a change in the pressure of a closed test tube, since no oxygen is being consumed. We can use this pressure change to monitor the rate of respiration and metabolic activity of the organism. Most of experiment about fermentation researched  and found mostly dealt with the fermentation of the common baking yeast S. cerevisiae in relation to temperature or change in pH that is why in this investigation we will see the effect of Sorbitol which a sugar substitute used in the production of lager beer and is present in these beer when they are going to be consumed.

After being exposed to high osmolarity, yeast cells accumulate high amounts of glycerol which serves as an osmolyte . Osmotic shock disrupts actin cytoskeleton and invaginations appears affecting the conformation of actin bundles that disturbs MAP kinase cascade, which regulates cell cycle . This also causes water to flow out of the cell, increasing the concentration of cellular components, including ion concentrations that can serve as a sensor for cellular signaling pathways . Under osmotic pressure, the excretion of ethanol and glycerol is impaired, leading the accumulation of intracellular ethanol and a decrease in cell viability .The concentration of Sorbitol in fermentation is important since Sorbitol is one of the main components in For the production of lager beer the use of sorbitol is one of the main components in lager Beer which is the type of beer produced by the yeast S. pastorianus which is the one being tested. The process of ethanol production for large beer producing companies is relevant to the maximization in the the production of beer so seeing if the concentration of sorbitol affects the rate of CO2 production is an important thing to take into account.



Hypothesis:If fermentation in a closed environment without oxygen present is made to proceed in different concentrations of sorbitol in the fermentation mixture from 0% to 10%  then the amount of CO2 produced will the the most and the fermentation will yield most product when the sorbitol has around 3% to 5% presence in the mixture because if the fermentation process is exposed to high amounts of sorbitol then the cell can go into  Osmotic shock which disrupts actin cytoskeleton and causes water to flow out of the cell, increasing the concentration of cellular components, including ion concentrations that can serve as a sensor for cellular signaling pathways.


Independent Variable: The tonicity of the environment in this experiment will the variable manipulated. There will be ten groups of  varying concentration of sorbitol from 1% to 10 % respectively obtained by mixing water with sorbitol to get the concentration desired for each trial.

Dependent Variable: The dependent variable measured will be the production of CO2 from the fermentation process measured in atm from the gas pressure sensor connected to the environment which has no known uncertainty.