What are the Types of Fermentation?

This word fermentation has been through several changes in terms of its meaning in the previous hundred years. If you look into the origin of this word, it represents gentle bubbling or boiling conditions. Notably, this meaning of fermentation was applied when it described the production of wine. Here, this bubbling was due to carbon dioxide. Moreover, this definition and types of fermentation have extended in recent years.

This extension happened first when a French chemist named Louis Pasteur went on to demonstrate that it was caused by yeast. Moreover, fermentation reactions can occur in any bacteria, which require an environment that is free of oxygen for its survival.

What is Fermentation?

Fermentation is a metabolic process. It causes chemical changes in organic substances with the help of enzymes. Moreover, it is a process where organisms convert carbohydrates into acid or alcohol. 

Common Fermentation Examples Are –

1. Yeast performing fermentation to obtain energy and in this process, converting sugar into alcohol. This is a very common phenomenon which can be observed often.

2. Bacterias use this process to convert carbohydrate into lactic acid.

Please note, the study of fermentation is called zymology.

Process of Fermentation

The pathway of fermentation regenerates coenzyme nicotinamide adenine dinucleotide (NAD+). This coenzyme is used in glycolysis, which releases energy as ATP. Additionally, fermentation yields 2 ATP per glucose molecule. 

Furthermore, the primary function that is related to fermentation is to transform NADH into the coenzyme known as NAD+. The primary reason being that it can be used for glycolysis. Notbaly, during this process, an organic electron acceptor which can be pyruvate reacts with the NADH to produce NAD+. Additionally, it generates products like carbon dioxide, lactate, or ethanol, etc.

Industrial Use of Fermentation

The fermentation process is vital for the beverage and food industry. The conversion of sugar into ethanol is used to make alcoholic beverages. Additionally, the carbon dioxide released by yeasts proves useful in the leavening of bread. Moreover, the organic acids derived from this process helps in preserving vegetable and dairy products. Here is a list of some conventional products that are derived from the application of fermentation –

• Wine

• Beer

• Cheese

• Yoghurt

• Specific foods products containing lactic acids like kimchi.

• Bread

Apart from these, the fermentation process also aids in hydrogen gas production and industrial alcohol production.

Definition and types of fermentation is a vital topic for NEET 2025. However, it is not a difficult chapter to prepare. Read on to know about the different fermentation processes in greater detail. 

Types of Fermentation Processes

There are several different types of fermentation processes, some of which are mentioned below. Notably, these are some of the most important ones –

Ethanol Fermentation

In the case of ethanol fermentation, this pyruvate formed via glycolysis is transformed into carbon dioxide and ethanol in two steps. These are –

1. The pyruvate begins by releasing carbon dioxide to produce a compound of two-carbon named acetaldehyde.

2. After that, acetaldehyde is decreased by NADH to form ethanol. It generates NAD+ for further use in glycolysis.

In a nutshell, this process converts a single molecule of glucose into a couple of molecules of ethanol and two more molecules of carbon dioxide. Moreover, yeast is responsible for ethanol fermentation.

Lactic Acid Fermentation

Broadly, there are two types of lactic acid fermentation which are homolactic and heterolactic. In the case of homolactic fermentation, pyruvate is reduced by NADH directly from lactate. Notably, this process does not go on to release any gas. Here, a single molecule of glucose transforms into a couple of molecules of lactate.

On the other hand, heterolactic fermentation is responsible for metabolising some lactates even further. It produces ethanol and carbon dioxide through the phosphoketolase pathway.

Particular bacteria and fungi perform this fermentation process. Furthermore, this fermentation process also occurs in body muscles to create ATP when its oxygen supply is low.

Alcohol Fermentation

The alcohol fermentation process helps in producing wine, beer, biofuel etc. Here pyruvic acid disintegrates into carbon dioxide and acetaldehyde. Furthermore, acetaldehyde produces ethanol, and NADH forms NAD+ for glycolysis. The penultimate product is carbon dioxide and alcohol.

Bacteria and yeast are primarily responsible for this process. Additionally, alcohol dehydrogenase and enzyme pyruvic acid decarboxylase catalyse this reaction. 

Hydrogen and Methane Gas Production

Various fermentation processes can produce hydrogen gas. In humans, hydrogen gas production happens due to intestinal bacteria. Apart from that, organisms use hydrogen gas to regenerate NAD+ from NADH.

Moreover, methanogenic archaea go through a disproportionate reaction where one electron gets transferred from a carbonyl of a carboxylic group to a methyl group of acetic acid. This process produces methane and carbon dioxide gas.

Other types of the fermentation process are acetic acid fermentation, butyric acid fermentation, etc. 

Prepare Well and Ace This Examination with Ease

As mentioned earlier, types of fermentation is a vital topic for NEET 2025, and questions have come from this chapter in the previous year’s exams. Additionally, it is not a very hard chapter to prepare, thereby making it one of the most scoring options.

As NEET 2025 is around the corner and the preparations have already started, you must stay fit and healthy in this period. Any health issue has the potential to hamper your final revision and exam preparation. 

Consequently, you should prepare a daily routine to help your studies. Moreover, do not forget to include the fermentation reaction in your revision, since you will face easy questions from this chapter.