Ethanol can be made by fermentation:
1. Fermentation uses yeast to convert sugars into ethanol. CO2 is also released.
sugar------>ethanol + carbon dioxide
2. The yeast cells contain zymase, an enzyme that acts as a catalyst in fermentation.
3. Fermentation happens fastest at about 30 degrees c. This is because zymase works best at this temp. At lower temps the reaction slows down. If the temp is too high the zymase is denatured (destroyed).
4. Zymase also work best at a pH of about 4 - a stongly acidic or alkaline solution will stop it working.
5. It's important to prevent oxygen getting to the fermentaion process. Oxygen converts the ethanol to ethanoic acid, which lowers the pH and can help stop the enzymes working.
6. When the concentration of ethanol reaches about 10 to 20%, the fermentaion reaction stops, because the yeast gets killed off by the ethanol.
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