The fermentation process simply explained:

The brewing of beer looks back on a long tradition. More than 8,000 years ago in the Neolithic Age, people knew how to make alcoholic beer from water and barley. What they did not know yet: Microorganisms, more specifically yeasts, decompose the carbohydrates of barley under anaerobic conditions to gain energy for their own metabolism. These processes are generally referred to as fermentation (English fermentation).
It took until the mid-19th century, before Louis Pasteuer could connect the fermentation process with microorganisms. He proved experimentally that microorganisms do not need oxygen for this. To date, it was still believed that living things could not survive without oxygen.
Pasteur also earned a reputation in other areas of biochemistry. Today's method of pasteurization, in order to preserve milk, for example, dates back to his research.
From an economic point of view, the fermentation process is not very effective for most microorganisms in terms of energy production. Therefore, fermentation also proceeds only in the absence of oxygen. On the other hand, if enough oxygen is available, the microorganisms resort to more effective processes, such as the respiratory chain. Approximately 30 ATP are produced per glucose molecule. During fermentation only 2 ATP.
Man can gain ATP from fermentation processes in deficiency situation in the muscles. This lactic acid fermentation, however, takes place without the involvement of bacteria.

Examples of fermentation processes

Alcoholic fermentation and lactic acid fermentation are the two best known fermentation processes. Mention should also be made of formic acid fermentation, butyric acid fermentation and propionic acid fermentation.
Alcoholic fermentationThe carbohydrates (glucose) are metabolized by microorganisms, preferably yeasts. The result is ethanol, carbon dioxide, water and ATP. Alcoholic fermentation plays a role especially in the production of beer and wine. The metabolism of baker's yeast, known as leavening agent for bread and rolls, also works by means of alcoholic fermentation.
Lactic acid fermentation: The carbohydrates are metabolized by lactic acid bacteria to lactate (lactic acid), hydrogen, water and ATP. Lactic acid fermentation is the basis for the production of sourdough (bread), buttermilk, yoghurt or quark.