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Ethanol fermentation, also called alcoholic fermentation, is a biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as by-products.
First, glucose metabolism is faster through ethanol fermentation because it involves fewer enzymes and limits all reactions to the cytoplasm. Second, ethanol has bactericidal activity by causing damage to the cell membrane and protein denaturing , allowing yeast fungus to outcompete environmental bacteria for resources. [ 6 ]
In ethanol fermentation, one glucose molecule is converted into two ethanol molecules and two carbon dioxide (CO 2) molecules. [10] [11] It is used to make bread dough rise: the carbon dioxide forms bubbles, expanding the dough into a foam. [12] [13] The ethanol is the intoxicating agent in alcoholic beverages such as wine, beer and liquor. [14]
Prior to Pasteur's research on fermentation, there existed some preliminary competing notions of it. One scientist who had a substantial degree of influence on the theory of fermentation was Justus von Liebig. Liebig believed that fermentation was largely a process of decomposition as a consequence of the exposure of yeast to air and water. [4]
Industrial fermentation is the intentional use of fermentation in manufacturing processes. In addition to the mass production of fermented foods and drinks, industrial fermentation has widespread applications in chemical industry. Commodity chemicals, such as acetic acid, citric acid, and ethanol are made by fermentation. [1]
Acetic acid bacteria (AAB) are a group of Gram-negative bacteria which oxidize sugars or ethanol and produce acetic acid during fermentation. [1] The acetic acid bacteria consist of 10 genera in the family Acetobacteraceae. [1] Several species of acetic acid bacteria are used in industry for production of certain foods and chemicals. [1]
The ABE fermentation via Clostridium beijerinckii or Clostridium acetobutylicum for instance is characterized by product inhibition. This means that there is a product concentration threshold that cannot be overcome, resulting in a product stream highly diluted in water. [11] Phase equilibrium diagram for 1-butanol–ethanol–water ternary mixture
The term "fermentation" sometimes refers specifically to the chemical conversion of sugars into ethanol, producing alcoholic drinks such as wine, beer, and cider. However, similar processes take place in the leavening of bread (CO 2 produced by yeast activity), and in the preservation of sour foods with the production of lactic acid , such as ...