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Investigation into the effect of different sugars on alcohol fermentation

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Introduction

Investigation into the effect of different sugars on alcohol fermentation. Abstract: This experiment was designed to test the effect of varying sugars on ethanol production, under anaerobic conditions. This was carried out by running a fermentation procedure for roughly a week, and distilling the resultant mixture, to determine the volume of ethanol produced. This experiment did provide realistic changes that can be made in the future, which should result in a more effective experiment. Aim: The aim of this experiment is to investigate the effect of different sugars on the production of ethanol in alcohol fermentation Rationale: Alcoholic fermentation occurs naturally in nature. It can also be utilised to produce alcoholic beverages in brewing and ethyl alcohols for industrial use. Fermentation occurs as the yeast join with the sugar molecules, and break them apart into other products. Enzymes work on a "lock and key" mechanism, by which only molecules with a perfectly matching active site can form an enzyme-substrate complex. This mechanism determines the effectiveness of the conversion of some sugars into the products. As enzymes can only form a complex with one type of molecule, there shall be some enzymes that cannot react with some of the sugars used in this experiment. For example, enzymes with the glucose matching active site cannot form a complex with lactose, and so on. Glucose Reaction: Glucose --> Ethanol + Carbon Dioxide C6H12O6 --> 2 CH3CH2OH + 2 CO2 The above reaction releases 118KJ/mol. Enzymes work by reducing the activation energy required in a reaction. This is the same function as a catalyst and enzymes are often referred to as "natural catalysts." This process of fermentation is most currently used in bread making, alcohol brewing and wine making. The alcohol produced during bread making is baked off and the CO2 produced is released into the atmosphere. In alcohol production, the ethanol is utilised to give the beverage alcoholic properties and the CO2 may be used to carbonate the drink. ...read more.

Middle

* The volume of sugar added to the fermentation mixture. Increasing the volume of sugar in the fermentation mixture will result in the sugar solution concentration increasing, increasing the rate of reaction. This will result in more ethanol being produced in a period of time, up until a point, at which the maximum speed of the yeast is reached. * The volume of yeast added to the fermentation mixture. Increased volumes of yeast will result in an elevated rate of reaction, resulting in larger volumes of ethanol being produced in shorter periods of time. * Temperature of distilling. Increasing the distilling temperature will result in more water vapour being produced, and mixing with the ethanol. This will result in there appearing to be more ethanol produced than is true. Ethanol can be diluted in water, so will not form a visible separate layer. A way of countering this is to re-distill the ethanol, to remove water impurities. This will produce more accurate results. Varying the temperature for different fermentation mixtures will result in varying quantities of water in each ethanol sample. * The length of time that each of the 50ml samples are distilled for. In order to perform all distillations in the 2 days allocated, the length of time for distilling needed to be limited. This was limited to 45 minutes each. Increased time for some of the distillations may result in there being higher quantities of ethanol distilled, affecting the reliability of the results. Hazards and Safety: Under the Control Of Substances Hazardous to Health (COSHH) some chemicals in use in this experiment need to be identified and handled carefully. Ethanol: * Highly flammable, should be kept away from naked flames or other ignition sources at all times. * Slightly toxic, should not be ingested, or inhaled. If any quantity of ethanol is ingested, large amounts of water should be consumed in order to dilute the ethanol. ...read more.

Conclusion

It is clear that lactose, a disaccharide, produced the largest volume of ethanol, due to its ability to form more molecules of ethanol than other sugars. In future experiments, the following alterations mustbe made, in order to attain more accurate results: * In order to attain more accurate results, the full fermentation mixture must be distilled, to ensure that all the ethanol is present in the distillation equipment, and the distillation should take place for longer. This will ensure that all of the ethanol is distilled, and total ethanol produced can be recorded instead of ethanol present in 50ml sample. * The fermentation mixture should be heated up to a higher temperature during the fermentation. This would speed up the rate at which the ethanol is produced, and save time, by not having to run the fermentation over the period of 1 week, the suggested temperature value is around 35�C, as this is the optimum temperature for brewers yeast. * The fermentation mixture should also be distilled for much longer, to ensure that all of the ethanol in the mixture has been removed, giving more accurate results. * The variation in the sugars should also be increased, to provide a broader spectrum from which results could be attained. This could further compound the theory that number of carbon atoms in ring is directly linked to the volume of ethanol produced. * More accurate measuring equipment. The measuring cylinder in which the ethanol was collected is only accurate to within 1ml and human error can often arise from misreading the volume. To overcome this, a more accurate form of measurement must be used, such as a small 5ml syringe, or 10 ml for larger volumes. The measurement levels are spaced much further apart on the syringes, so more accurate readings can be taken. * The fermentation mixture should also undergo vacuum filtration before being placed into the distillation equipment. This will prevent any damage to the distillation equipment, and will also reduce the distillation time as there is less solid matter in the mixture. ...read more.

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