Fermentation

What is Fermentation?

Fermentation is the process of releasing energy from glucose when oxygen is unavailable. The process of Fermentation takes place in yeast cells, bacteria, and in animal muscles. 

Respiration that occurs at the smallest level of our bodies – in the cells – is Cellular respiration. This can take place in the absence or presence of oxygen. In cellular respiration, Glycolysis is the first step. As an end result of this process, Pyruvic Acid (a 3-C molecule ) is formed. However, this pyruvic acid is managed differently by various cells. One of these is fermentation. 

Let’s take a closer look at fermentation, anaerobic respiration and the various types of fermentation.

Anaerobic Respiration 

This is a form of respiration where oxygen is deficient. In several eukaryotes and prokaryotes, an anaerobic pathway known as fermentation, is a common process that is found. This process involves the partial oxidation of glucose to form alcohol and acids.

In yeast organisms, carbon dioxide CO₂ and ethanol is the final result of conversion of partial oxidation of glucose that forms pyruvic acid. The enzymes – alcohol dehydrogenase and pyruvic acid decarboxylase – are the catalysts for the process. This is known as ethanol fermentation or alcoholic fermentation. 

Pyruvic acid, in anaerobic environments, is converted to lactic acid in some bacteria as well as in animal muscle cells. This is known as lactic acid fermentation. These anaerobic fermentations can result in dangerous end results. For instance, the potency of alcohol produced by yeast cells when higher than 13 percent might result in killing them.

In the fermentation of alcohol and lactic acid, the reducing agent is NADH+H which is then oxidized into NAD +. Both these processes release very little energy. There are only two ATP molecules that are produced during this fermentation. This is much lower when compared to aerobic respiration.  

However, this fermentation process is widely used in the pharmaceutical and food industries.

There are three types of Fermentation:

Fermentation of Lactic Acid

This is when starch or sugar is converted to lactic acid by bacteria and yeast strains. Physical exercise increases energy expenditure faster than oxygen supply to muscle cells in the body. This causes lactic acid to form and can cause painful muscles.

Fermentation of Acetic Acid

Vinegar and condiments are made from starch and sugar found in fruits and grains. E.g. apple cider vinegar.

Fermentation of Alcohol

The end product of glycolysis – Pyruvate – is converted into alcohol and carbon dioxide. Alcoholic fermentation is responsible for the production of wine and beer.