Fermentation of Yeast Lab Report

Design

Aim

To investigate the relationship between the amount of sugar used in fermentation and the amount of ethanol produced

Research Question

1.      How does the amount of sugar used in fermentation affect the amount of alcohol produced?

2.      Is the usage of more sugar as effective as the usage of less sugar in the fermentation with 2g of yeast?

Hypothesis

The amount of ethanol produced increases along with the amount of sugar used

The increase of the amount of sugar allows the yeast to convert more sugar into ethanol, causing the amount of ethanol to increase

Variables

	Variables	Ways of Preparing Variable
Constant	The amount of yeast used	The same amount of yeast is prepared by using the same mass measured with an electronic balance
Manipulated	The amount of sugar used	The sugars are increased by 0.02mol each experiment and measured using M/Mr to find out the mass
Responding	The amount of ethanol produced	Ethanol collected through distillation at 78°c

Apparatus

1.      5 250ml Conical Flask

2.      Boiled glucose solution

3.      10g of yeast

4.      100ml measuring cylinder

5.      1 Stopper

6.      1 Thermometer

7.      1 Liebig Condenser

8.      1 Fractionating column

9.      Retort stands and clamps

10.  1 Florence flask

11.  2 1m Rubber tubing

12.  2 filter funnels

13.  1 Boiling tube

14.  36g of fine sugar

15.  1 Spatula

16.  1 Glass rod

17.  1 Electronic balance

18.  1 Evaporating dish

19.  1 Water bath

Procedure/ Method

1.      Prepare apparatus for fermentation (2g of yeast, 100ml of water, 1 250ml Conical Flask, 1 Stopper)

2.      Prepare 0g of sugar

3.      Mix sugar with 100ml of water in conical flask

4.      Stir solution until no white particles are visible

5.      Insert 2g of yeast

6.      Stir solution until yeast is fully dissolved

7.      Insert Stopper

8.      Leave solution for 1 day for fermentation process

9.      Prepare apparatus for distillation (Retort stands and clamps, 1 Florence flask, 1 Liebig condenser, 1 thermometer, 1 water bath, 2 1m rubber tube, water source)

10.  Attach 1 rubber tube from Liebig condenser to water source input

11.  Attach 1 rubber tube from Liebig condenser to water output

12.  Immerse Florence flask in water bath at 78°c

13.  Collect and measure ethanol produced with measuring cylinder

14.  Record data by using an ethanol produced/ amt. of sugar used graph

15.  Repeat step (1-14) 5 times with an increase of 0.02mol of sugar used in experiment

Safety Procedures

1.      Experiment must be done under teacher’s supervision

2.      Estimated concentration of alcohol should not exceed 50%

Data

Overview

Data is recorded with tables and graphs to observe changes and identify traits.

Amount of Sugar needed

Mol. Of Glucose (C6H12O6)	Calculation (M= mol. x Mr, Mr= 180g)	Amount of Sugar Needed (g)
0	0.00 x 180	0
0.02	0.02 x 180	3.6
0.04	0.04 x 180	7.2
0.06	0.06 x 180	10.8
0.08	0.08 x 180	14.4

Amount of Alcohol Produced

Amount of Sugar used (g)	Amount of Yeast used (g)	Amount of Alcohol Produced (ml)
0	2	0
3.6	2	1.2
7.2	2	1.8
10.8	2	2.5
14.4	2	0

Observation

From the graph, the rate of total amount of alcohol produced increases as the amount of sugar used in the experiment is increased. According to the R² value obtained through excel, the percentage of yield of the activity of yeast in our experiment is 97%. The last result in the experiment is excluded from the graph due to inaccurate data obtained. A fragrance smell of alcohol is given out when the end product is produced.

Data Analysis

  Ethanol Fermentation is a process where glucose is converted into cellular energy in the form of ATP to provide energy for the yeast in the absence of oxygen to produce ethanol and carbon dioxide as metabolic waste products.

  The glucose first undergoes glycolysis. With the addition of 2 ATP molecules, a phosphate group is formed and joins with glucose to form fructose diphosphate along with the by-product of 2 low energy molecules called ADP. The 6 carbon chain glucose is then broken down into two 3 carbon chain molecules to form sugar phosphate. The sugar phosphates then undergo a series of reactions to be converted into pyruvic acid.  In the course of these reactions, the electrons of both molecules are transferred to the co-enzyme NAD⁺ (nicotinamide adenine dinucleotide) to form 4 molecules of ADP.  4 molecules of ADP combine and form ATP. In this reaction, there is a net gain of 2 ATP in this process excluding the sacrificial amount of 2 ATP molecules for glycolysis to occur.

The chemical equation of glycolysis is:

C₆H₁₂O₆ + 2 ADP + 2 P_i + 2 NAD⁺ → 2 CH₃COCOO⁻ + 2 ATP + 2 NADH + 2 H₂O + 2 H⁺

  These ATP molecules are provided to the yeast and with no oxygen provided; the cellular energy is not processed completely hence, instead of converting ATP into water and carbon dioxide, the yeast performs an incomplete conversion producing ethanol and carbon dioxide.

C₁₀H₁₆N₅O₁₃P₃ → C₂H₅OH + CO₂

         (Yeast)

  The yeast does not affect the increase of rate in the amount of alcohol produced as it acts as a catalyst in the reaction. A catalyst does not act as a limiting reagent as it is either reacted and reformed later in the reaction or doesn’t react in the reaction. Therefore, the result is in linear graph form. With the more amount of sugar added into the experiment, more ethanol will be produced.

Evaluation

1.      Data 4 (highlighted in red) is eliminated from the trend line graph due to contact of the yeast with oxygen in the middle of the experiment. This was caused by the pressure of CO₂ made by the yeast had forced the stopper out, allowing oxygen to enter.

2.      Measurements error might be made as the 100ml measuring cylinder is not ideal for measurements of small amount of substances

Improvements to be made

1.      A transport tube located on top of the stopper immersed in limewater for CO₂ should be used to transport carbon dioxide out of the flask to maintain pressure

2.      A pipette should be used to measure small amounts of substances below 100ml for more accuracy

Conclusion

The hypothesis “The amount of ethanol produced increases along with the amount of sugar used” is proven from the experiment which also justifies that catalysts, yeast, does not affect the products of the experiment.