Реферат: Fermentation Essay Research Paper PlanningPROBLEM TO BE

Fermentation Essay, Research Paper



Yeast enzyme specificity: Specificity of Brewers and Bakers yeast enzymes to different sugars (being monosaccharides)


I predict Bakers yeast to have a different enzyme specificity compared to Brewers yeast where more CO2 is produced at 37 0C.


Fermentation is the breakdown of sugars by bacteria and yeast using a method of respiration without oxygen (anaerobic respiration). It involves a culture of yeast and a solution of sugar, producing ethanol and carbon dioxide with the aid of the enzymes.

As a culture of yeast is merged with solution of sugar, a reaction called fermentation occurs. As products, ethanol and carbon dioxide are produced, in form of liquid and gas respectively. The reaction follows this equation:

Glucose solution + Yeast Carbon dioxide + Ethanol + (Energy)

As one of the products is in the form of gas, the volume of the product can be measured to demonstrate the difference of the reaction when certain factors are changed. In the other words, the rate of reaction can be illustrated by doing appropriate calculation involving the volume of gas produced, in this case the amount of Carbon Dioxide produced.

This process can be slowed down by denaturation of the enzymes at a certain temperature.

Method and Apparatus

+ Polypropylene test tube rack in order to hold all the test tubes

+ 5 fermentation tubes to allow the fermentation process to be carried out.

+ 5 test tubes to hold the fermentation tubes.

+ A pencil to hold fermentation tubes when the test tube is inverted

+ A ruler with mm scale in order to measure the CO2 bubble

+ Brewers yeast and Bakers yeast (20% solution {20g/100cm3})

+ Distilled water as a control experiment

+ 20% solutions of Glucose, sucrose, fructose and galactose (20g/100cm3)

Label five fermentation tubes 1-5, writing the numbers with a wax pencil upside down near the bottom of each tube. Pipette the following into each tube (10 drops of distilled water, glucose, fructose, sucrose, and galactose). Set up the fermentation tubes as follows. Hold the filled tube in your hand and insert it into an inverted test tube. With a pencil, or some other suitable instrument, push the small tube into the inverted test tube as far as it will go and then invert the whole assemblage so that the contents in the fermentation tube does not spill out. Tap the outer tube firmly to release any bubbles (CO2) trapped at the mouth of the inner tube. When all fermentation tubes have been set up, record the height of the fluid in mm in each one. Do this by holding the test tube vertically on a table ands placing a millimetre ruler alongside it. Now place all the test tubes in a constant-temperature water bath at 37 0C for 10 minutes. Remove the test tubes from the constant-temperature bath, and re-measure the height of the fluid in each fermentation tube. If enough gas has collected in the fermentation tube to make it buoyant, you must push it down when taking your reading. Record the difference in height between the initial and final reading for each of the tubes.

Measurements, Observations and Controls

I shall repeat this experiment 10 times for each sugar and both yeasts, which will give me about 80 raw data results. The accuracy will be to nearest 2 decimal places in mm.

A T-test will also be carried out after all raw pieces of data have been collected and been inputted into a suitable table. A graph will then be plotted to show enzyme specificity in Brewers and bakers yeast that have been tested in glucose, galactose, fructose and sucrose

All variables will be controlled. The temperature, at which the yeast will react during the fermentation process, will be controlled using a water bath at a constant temperature of 37 0C. The CO2 bubble in the fermentation tube will be measured with a ruler with a mm scale on it.

Risk Assessment and Ethical implications

A warm water bath will be used which may be slightly dangerous in that you can be burnt, I will be dealing with an electrical device therefore I should take great care not to touch plugs with wet hands.

I will be using living organisms (yeast) in my experiment however they will not be killed for or during the experiment.

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