Ethanol and Fermentation Chemistry PDF

Ethanol and Fermentation Chemistry biochemistry Fermenation: grain alcohol processes involved in making bread, making wine, and brewing In 1810, Gay-Lussac discovered the general chemical equation for the breakdown of sugar into ethanol and carbon dioxide Pasteur demonstrate...

Ethanol and Fermentation Chemistry biochemistry Fermenation: grain alcohol processes involved in making bread, making wine, and brewing In 1810, Gay-Lussac discovered the general chemical equation for the breakdown of sugar into ethanol and carbon dioxide Pasteur demonstrated that yeast was required in the fermentation His results were published in 1857 and 1866. Fermenation: active catalyst of bio- chemical origin, the enzyme zymase zymase acts on only a few select sugars and not on all carbohydrates; the digestive enzymes of the alimentary tract are equally specific in their activity. grain alcohol- ‫ممكن تجيب بقايا الفواكه‬ ‫وتخمرها‬ starch has been converted to the sugar maltose by hydrolysis of ether and acetal bonds. This solution is known as the wort. Industrial scale Most industrial ethanol in the United States is now manufactured from ethylene, a product of the “cracking” of petroleum hydrocarbons. By reaction with concentrated sulfuric acid, ethylene becomes ethyl hydrogen sulfate, which is hydrolyzed to ethanol by dilution with water. The al- cohols 2-propanol, 2-butanol, 2-methyl-2-propanol, and higher secondary and tertiary alcohols are also produced on a large scale from alkenes derived from cracking Yeasts, molds, and bacteria are used commercially for the large-scale produc- tion of various organic compounds. An important example, in addition to etha- nol production, is the anaerobic fermentation of starch by certain bacteria to yield 1-butanol, acetone, ethanol, carbon dioxide, and hydrogen. sucrose Disaccharides = glu+fruc: formula C12H22O11 Drawbacks = disadvantags The fermentation is inhibited by its end product ethanol it is not possible to prepare solutions containing more than 10–15% ethanol by this method More concentrated ethanol can be isolated by fractional distillation. Ethanol and water form an azeotropic mixture consisting of 95% ethanol and 5% water by weight Procedure & equipment An incubator : 30-35 °C Place 2.00 g of sucrose in a 50-mL Erlenmeyer flask Add 18.0 mL of water warmed to 25–30°C, 2.0 mL of Pasteur’s salts Add 0.2 g of dried baker’s yeast Shake the contents vigorously to mix them Allow the mixture to stand at about 30–35°C for 1 week Fractional Distillation at 78 °C Then measure the density ~0.78 g/ml- 0.80 g/ml Analysis of Distillate QUESTIONS  Uses: Ethanol is present in alcoholic drinks (beer, wine, spirits) when diluted. It is used as a topical agent to prevent skin infections, in pharmaceutical preparations (e.g. rubbing compounds, lotions, tonics, colognes), cosmetics, and in perfumes. Ethanol may be present in fuels, Discussion: Factors Affecting Fermentation: temperature, pH, and sugar concentration , osmatic stress can affect yeast activity and ethanol yield. Several factors can contribute to discrepancies between the theoretical and actual yields of ethanol: 1 Contamination: The presence of unwanted microorganisms can lead to competition for sugars and the production of other fermentation products, further decreasing the yield of ethanol. Incomplete Fermentation: Not all sucrose may have been converted into ethanol due to insufficient fermentation time, suboptimal conditions (temperature, pH), or nutrient deficiencies. If the fermentation process was stopped too early, some sucrose would remain 1 Yeast Viability: The health and viability of the yeast used in the fermentation process are critical. If the yeast was old, improperly stored, or stressed by high sugar concentrations or temperature fluctuations, it may not have performed optimally, leading to lower ethanol production. 1 Byproduct Formation: During fermentation, yeast can produce various byproducts (e.g., glycerol, acetic acid, and higher alcohols) instead of ethanol. If the fermentation conditions (such as temperature and nutrient availability) are not ideal, yeast may divert metabolic pathways toward byproduct formation, reducing the amount of ethanol produced.