Etanoolkäärimise

Etanoolkäärimine, also known as alcoholic fermentation, is a biological process that converts sugars into ethanol and carbon dioxide. This process is carried out by various microorganisms, primarily yeasts, in the absence of oxygen. It is a fundamental metabolic pathway used in the production of alcoholic beverages like beer, wine, and spirits, as well as in the leavening of bread.

The key enzymes involved in ethanol fermentation are typically found in the cytoplasm of the yeast cell. The initial step is glycolysis, where glucose is broken down into pyruvate. Pyruvate is then converted into acetaldehyde, releasing carbon dioxide. Finally, acetaldehyde is reduced to ethanol by the enzyme alcohol dehydrogenase, using NADH as a cofactor. The regeneration of NAD+ from NADH is crucial for glycolysis to continue.

Different yeast species can ferment different types of sugars. For instance, Saccharomyces cerevisiae is commonly used in baking and brewing because it efficiently ferments glucose, fructose, and sucrose. Other microorganisms, such as certain bacteria and even some plant tissues, can also perform ethanol fermentation under anaerobic conditions, though their metabolic pathways and products may vary. The efficiency and end products of ethanol fermentation can be influenced by factors like temperature, pH, and the presence of inhibitors. This process is vital for many industries and has been utilized by humans for millennia.