Ethanol production by fermentation at the optimal temperature Lee, W. van der & Velden, M. van der Pallas Athene College Ede, The Netherlands Received April 2010 Summary Because all interest we put in alcohol, we now look closer to the production of it, in a scientific way: the production of ethanol. In an old chemical process ethanol is produces by use of yeast and sugars. This process is called fermentation. The yeast will ferment the sugar into ethanol and carbon dioxide. Fermentation is an anaerobic process, which concludes no oxygen is needed. This means that other factors affect the amount of ethanol production. Because the temperature affects many chemical processes, we are going to look whether a special temperature gives an optimal production of ethanol, or in a more easily way to measure: the production of carbon dioxide. The process was followed at temperatures of 35, 37, 39°C. The most optimal production was found at a temperature of 35°C, but it also raised further questions, like why 37°C is the less optimal temperature for the carbon dioxide production. We found an amount of carbon dioxide that was less than optimal. © 2010 Pallas Athene College. All rights reserved. Introduction All over the world during many ages in history, alcohol was produced. From the old Greece until even a story from the Bible we can find alcohol among us. The scientific name of alcohol is ethanol, CH3CH2OH. The most common synthetic alcohol is produced by a reaction between ethane and water: CH2=CH2 (g) + H2O (l) CH3CH2OH (l). Because of the effectively benefit this reaction has, one prefers this one, however during mankind’s population growth, crude oil, the source of ethane, will run short. Reason to look at another chemical process for the ethanol production , namely fermentation. Fermentation is the biochemical reaction to convert biological materials into other substrates by use of bacteria, fungi, enzymes etc. in an oxygen free (thus anaerobe) environment. One of such processes from fermentation is yeasting. Here is sugar converted into ethanol (!) and carbon dioxide. The following reaction will make clear that no oxygen is needed: C6H12O6 (s) CH3CH2OH (l) + 2CO2(g). One of all kinds of sugar which will be most likely to use for fermentation, is the most commonly known D-glucose (dextrose), alias grape sugar. Dglucose is a mono-sugar. Other mono-sugars like Dfructose and D-mannose are suitable for fermentation too. Some sugars as disaccharides and polysaccharides must firstly be converted by hydrolysis. Sucrose for example, the disaccharide found in beet sugar and molasses, can be hydrolyzed into glucose and fructose by invertase. Invertase is an enzyme which can be found in yeast. The yeast species Saccharomyces cerevisiae has been used in baking and fermenting alcoholic beverages for thousands of years. These specie is also applied in research for fermentation. In the second reaction equation right above ‘C6H12O6 (s) CH3CH2OH (l) + 2CO2(g)’ one can see there is absolutely no oxygen needed for the yeast cells to grow on the sugar. CO2 production CO2 pruduction (g) 2,500 2,000 Our interest in yeast cells raised many questions. One which answer benefits the productivity of the ethanol production is: what temperature is the optimal temperature for the ethanol production by fermentation? Our hypothesis about that question is that it will be around the body temperature, because yeast cells are eukaryote living organisms which are like enzymes etc. and work optimal at a temperature around the 37°C temperature. This, or our experiment is untrustworthy. Experimental design Evaluation First we prepared a 18% D-glucose solution by putting 18 gram D-glucose and 0,125 gram yeast cells together and filling it with water till 100 mL. We did this six times, for six erlenmeyers. The erlenmeyers were labelled with the right temperature; two erlenmeyers with 35 °C, two with 37 °C, and 2 with 39 °C parafilm were put on the erlenmeyers and tiny holes were pierced through them. We weighted them all and put them in an area with the right temperature. The bottles were kept there for a couple of days and were weighted again. The difference in mass was calculated. This procedure was repeated with one erlenmeyer instead of two. During the weighting, we discovered that the erlenmeyers which were put in an 37 °C area, had become slightly heavier. We wondered if it had anything to do with the fact that they were being put in a water bath, and not, like the others, in a incubator. Was there a possibility that some water had sneaked through the tiny holes in the parafilm? Or was there both an inaccuracy in the weighting and an unforeseen fact that at 37 °C yeast cells produce less gas than at 35 and 39 °C? 37 39 1,000 0,500 0,000 34 35 36 37 38 39 40 Temperatuur (°C) So for improvements maybe we could examine whether the water bath does matter or not. Bibliography http://www.yeastgenome.org/VLwhat_are_yeast. html Results Temperature (C) 35 1,500 Mass Lost (g) 2.216 2.231 2.623 0.144 0.089 0.406 Averaged 2.357 1.717 2.076 2.605 2.133 http://www.yobrew.co.uk/fermentation.php http://www.newton.dep.anl.gov/askasci/mole00/ mole00195.htm 0.213 http://herbarium.usu.edu/fungi/funfacts/Fermenta tion.htm Discussion and conclusion According to the results, the amount of produced CO2 was the highest at 35 °C. This means the production of ethanol is the highest at 35 °C, too. So it was not at 37 °C, what we expected. Probably, yeast cells do not work optimal at body