Issues surrounding asexual reproduction
Economical = as yeast reproduces asexually during the brewing process the brewery ends up with a lot more yeast than necessary. This could become a waste issue. However the brewery actually sells the yeast off to other companies to make an extra profit. Bakeries, for example, which use yeast in the production of bread. This is economically advantageous. [4]
Environmental = because the brewers don’t throw away the excess yeast they produce they become environmentally friendly, as less waste is then created, which is better for the environment. [4]
Ethical = yeast reproduces asexually, this means there is no variation, every cell is exactly the same unless a mutation occurs. As breweries only want certain types of yeasts to make certain tastes and textures other yeasts are not used left to become extinct. Some would say this is unethical of the brewery to pick and chose which yeasts survive and which become extinct and that every strand of yeast should have the same chance of survival.
Second aspect: Fermentation
Fermentation is a chemical process that has been used for thousands of years to produce alcohol and is still now used in the modern brewing process. Fermentation can be defined as the anaerobic conversion of sugar to carbon dioxide and ethanol by yeast. To turn the sugar from the wort (glucose) into ethanol and carbon dioxide the yeast uses an enzyme to break down the sugar molecules. The yeast in this conversion is an agent which just allows the break down to take place without being used up itself. In the actual brewing process fermentation is the sixth process to take place. [2, 4, 6]
Issues surrounding fermentation
Environmental = the brewers do not let carbon dioxide given out from the break down of yeast escape into the atmosphere as it is a green house gas and therefore linked to global warming. Instead they collect the gas and convert it into liquid for the use of making drinks fizzy. This is also economically efficient for the brewery as they can use the carbon dioxide they collect to make their own beer fizzy without having to pay for it. [2, 4]
Social issues = the main products of the brewing process are beers, spirits, and wines. Alcoholic drinks are harmful when consumed in excess. Excess alcohol can alter judgment and can lead to dependency and other health related problems. “Taking more than one drink per a day for women or two drinks per a day for a man can raise the risk of breast cancer, motor vehicle crashes, high blood pressure, a stroke, and violence” etc. “Alcohol consumption during pregnancy increases the risk of birth defects.” One could say that these reasons alone are enough evidence to claim that the process of fermentation shouldn’t take place. [1]
Ethical = as yeast is a living organism some might say that allowing yeast to die after it has completed its task is unethical. However I do not agree with this as yeast is a single celled organism and is therefore not complex enough to feel pain.
Fermentation vessels
The biology behind the fermentation process
The process of malting releases enzymes such as alpha amylase from the germination of barley seeds which breaks down the starch to sugars for fermentation in the mashing process. Since most yeast are unable to breakdown starch the process of malting is essential for the brewing process. The sugars released from the breakdown of starch include glucose which is used by yeast in the bio-chemical process of fermentation to form ethanol and carbon dioxide. [5]
The first step in the fermentation process is the conversion of glucose to pyruvate (also known as pyruvic acid) in a process known as glycolysis. Glycolysis is a multi-step process that occurs in the cytoplasm of cells and involves 10 different enzymes. During the process two molecules of ATP are formed along with 2 molecules of pyruvate, equation 1 below:- [5, 6]
Equation 1: the general formula for glycolysis
Each molecule of pyruvate is then converted into one molecule of acetaldehyde and one molecule of carbon dioxide by the enzyme Pyruvate decarboxylase, shown in equation 2 below:- [5]
Equation 2
Finally the acetaldehyde is converted into ethanol by the enzyme Alcohol dehydrogenase, which in turn oxidises one molecule of NADH to NAD+, equation 3 below:- [5]
Equation 3
As a result one molecule of glucose (C6H12O6) is broken down into two molecules of ethanol (C2H5OH) and two molecules of Carbon dioxide (CO2) and causes the formation of two molecules of ATP, shown in equation 4 below:- [5, 6]
Equation 4: the overall formula for fermentation by yeast.
For the yeast the most important of these products is the ATP which supplies energy used for growth and reproduction. Without the process of fermentation yeast would die in anaerobic conditions. In fact ethanol is toxic to most eukaryotic cells, which include yeast. Hence when left in the presence of ethanol the yeast start to die. [5]
Conditions for Fermentation
Beer uses one of two major types of yeast: top fermenting yeast or bottom fermenting yeast. The main difference between the two is that top-fermenting yeast remain mainly uniformly distributed within the fermenting wort and are carried to the top of the fermentor by carbon dioxide gas formed as a product of fermentation. However bottom fermenting yeast settle to the bottom of the fermentor and do not rise using carbon dioxide. Top yeast are mainly Saccharomyces cerevisiae and used for the brewing of ales. However bottom yeast are mainly Saccharomyces carlsbergensis and used for the brewing of lagers. [4, 5]
Top fermentors tend to require higher temperatures then that of bottom yeast, at around 14-23oC and is accomplished in a shorter time, around 5-7 days. This is compared to bottom fermentors which work optimally at around 6-12oC and take around 8-14 days to complete the fermentation process. The control of heat within the fermentation vessel is an important factor in the fermentation process. Large fermentors store large amounts of yeast, which build up large amounts of heat that can in turn affect the efficiency of the fermentation process. It is therefore vital that the temperature within the fermentors is kept at a constant temperature. [4, 5]
As well as temperature several other factors need to be monitored during the fermentation process. Including: avoiding contamination from other micro-organisms, control of anaerobic conditions, control of pH, consistent wort quality. [4, 5]
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Future developments
One future development that the scientists who work at the Coors brewery are working on is the huge amount of space it takes to grow the barley needed to produce the glucose, and the pesticides sprayed on the land to make them grow. One was they are trying to overcome these problems is obtaining glucose from cellulose instead of starch. Cellulose can be obtained from other industries waste products e.g. sawdust and straw. The implication for the world of this development would be less production of waste as using other businesses waste products would be environmentally friendly and economically advantageous as well as also not using pesticides on the land which can cause havoc to natures balance. However this could drive the cost of alcohol down which could lead to an even bigger binge culture in Britain. [4]
Another future development of fermentation involves scientists in America trying to produce yeast which will allow glucose to break down faster into the ethanol wanted. This means more ethanol can be produced in a smaller amount of time. This means a brewery can produce more alcohol without investing more money in new machinery. The implications of this could have serious affects on the world. If more alcohol can be produced more quickly, this would cut the price of alcohol. People would drink more and would most certainly lead to more health problems within Britain. This inevitably would lead to major health problems and a crisis within the NHS. [2]
Bibliography
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accessed ion 17/1/06
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Madigan, M. T., J. M. Martinko and J. Parker, Brock Biology of Microorganisms, 10th Edition, 2003, Pearson Education Inc
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Solomon E. P., L. R. Berg and D. W. Martin, Biology, 6th Edition, 2002, Thomson Brook/Cole
Validity of my sources
This first of my resources is from the American Council on Alcoholism (ACA). This is an organization dedicated in bringing awareness about alcoholism and prompts a need for treatment. Whereas this may be morally and ethically correct the opinion of this group is not without bias and therefore brings the validity of this site into question when being used in an unbiased scientific report, I did find other sources supporting the ACA’s claims when looking into the reliability of my information, NHS leaflets supported the claim that alcohol does the body no good. However other reports with the opposite opinion such as finds scientific evidence to support their claims also therefore I cannot be certain which source is in the right.
Another questionably resource comes from the Coors brewery. Unlike the ACA they want to promote the production and distribution of alcoholic beverages in the aim of making more money. This therefore makes them bias towards brewing and alcohol fermentation unlike the ACA. Again I found a number of sources to support Coors claims such as .
The last of my two resources, 5 and 6, are well established scientific books written and published by well known scientific personal. These books aim to bring direct unbiased scientific facts. They therefore bring the most accurate and reliable information for this report. I have found other books and websites which authenticate the information in these books, is one such website, and this gives me confidence that what I have written in this report is reliable and accurate.
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