Fermentation is commonly defined as the process in which energy is formed by the process of oxidation of organic compounds like carbohydrates and sugars. This leads to conversion of these organic compounds into an acid or an alcohol which provides energy. It can be carried out by microorganisms with the help of oxygen, as well as without it. When fermentation is carried out in the presence of oxygen, it is called aerobic fermentation and when carried out without it, it is commonly known as anaerobic fermentation.
Equation of Anaerobic Fermentation
It can be supported with the help of an equation that describes the substrates used in the fermentation process to give the desired products. One of the examples is alcoholic fermentation whose equation is as given below:
Acetaldehyde + NADH + H+
Alcohol + NAD+
» In this reaction, anaerobic respiration occurs in the sugar (to cause fermentation) with the help of the fungus yeast, which doesn't come in contact with the atmosphere or oxygen. Acetaldehyde and NADH are the substrates of the reaction that are fermented along with one hydrogen ion to form the product, which is alcohol.
» This reaction takes place in presence of the active enzyme alcohol dehydrogenase to produce alcohol and a cofactor, which is an ion of NAD. This reaction follows the decarbaxylation of pyruvate with the help of the enzyme pyruvate decarboxylase, thiamine pyrophosphate (TPP), and two Mg ions. On completion of this phase, acetaldehyde and CO are formed to give the above-mentioned reaction.
Glycolysis, which is defined as the process of converting glucose to pyruvate, can happen by the anaerobic way. This pathway or transformation of glucose into pyruvate in the presence of very limited amount of oxygen is known as the anaerobic glycolysis.
The word 'lysis' means breakdown and 'glyco' means glucose, so from this pathway there is fermentation or breakdown of glucose to pyruvate which is a by-product of the same. This process produces energy (38 ATP molecules) in about 10 seconds to 2 minutes and is carried out in the cytoplasm of muscle cells. This energy is stored in the golgi apparatus inside these cells and then transported, as and when required throughout the body.
- Anaerobic glycolysis starts when glucose is phosphorylated into glucose-6-phosphate in the first step. Then this product is further converted into fructose-6-phosphate, which is then converted into fructose-1,6-bisphosphate.
- This product then gives two further products, viz., PGAL and DHAP, which are interconvertable by a reversible reaction.
- The PGAL then produces 1,3-bisphosphoglycerate by reducing one ion of NAD and an inorganic phosphate to NADH.
- This is then followed by the production of 3-phosphoglycerate and 2-phosphoglycerate one after the other, with the formation of 1 ATP molecule.
- The 2-phosphoglycerate then gives phosphoenolpyruvate (PEP) by dehydrogenation of one water molecule. This PEP is converted to pyruvate with the generation of another ATP molecule and, thus, energy is produced by anaerobic fermentation of glucose.
PicklingPickling is often called corning or brining. It is called so because foods like raw mangoes and cucumbers are preserved by the fermentation process, in a solution of salt and water called brine. This process can preserve perishable food for months without decaying. These brine tanks have closed lids so as to avoid contact with oxygen, as that may add other unwanted microbes to grow on the pickles and give a mixture of aerobic and anaerobic fermentation. This strategy of storing foods is very helpful for preserving perishable fruits and vegetables, which can then be eaten all year round.
As everyone knows the fact that fermentation is a very old concept, which finds its implementation in all the cuisines throughout the world, don't be afraid to eat those yummy pickles!