Define Fermentation | What is Fermentation? Types, History, Advantages - YB Study -->

Define Fermentation | What is Fermentation? Types, History, Advantages

What is Fermentation? Definition, History, types, Advantages

Definition of Fermentation : 
  • Fermentation is a process in which complex substances is converted into simple substances with the help of microorganisms.
  • Fermentation is an anaerobic process in which energy can be synthesized by converting carbohydrate, such as sugar and starch into alcohol and other compounds by microorganisms.
  • Fermentation is a chemical reaction in which sugars are broken down into smaller molecules by bacteria and yeast.

What is Fermentation?

  • Fermentation is a biochemical process in which complex organic substances is converted into simple substances with the help of bacteria yeasts and other microorganisms is known as fermentation.
  • The word fermentation is derived from the Latin verb fervere, which means to boil. 
  • Study of fermentation is known as Zymology.

  • In 1857 French chemist and microbiologist Louis Pasteur firstly used the term fermentation, he discovered that microorganisms, such as bacteria and fungus (yeasts) can cause fermentation.

  • Louis Pasteur was the first to demonstrate practically that fermented beverages are the result from the action of living  yeast which converts glucose into ethanol.

  • Louis Pasteur is known as father of fermentation. 

  • Fermentation process  is carried out in special type of vessel known as Fermenter or Bioreactor.

  • Bioreactor is defined as a vessel that carries out a biological reaction and it provide a controlled environment such as temperature, pH, substrate, salts, vitamins, oxygen etc for growth of microorganisms and product formation. 

  • There are different  types of bioreactors. The major types are: Continuous Stirred Tank Bioreactors, Bubble Column Bioreactor, Airlift Bioreactors, Fluidized Bed Bioreactors, Packed Bed Bioreactors etc.

  • There are different types of fermentation on the basis of Media, type of fermenter and type of end products. 

  1. On the basis of Media / Substrates there are two types of fermentation solid state fermentation and Submerged fermentation. 
  2. On the basis of type of fermenter there are two types of fermentation Batch fermentation and continuous fermentation.
  3. On the  basis of end product  fermentation is of two types Aerobic fermentation and Anaerobic fermentation.

  • Fermentation process is used for the production of alcoholic beverages like beer, wine, ethanol, bread, yogurt, vinegar and kombucha  and acetic acid, citric acid, gluconic acid, antibiotics, vitamins (Vitamins B12 &  B2) etc.

History of Fermentation 
Humans have a long history of using microbial fermentation to make food and drinks for thousands of years, but people have not fully understood the fermentation process before. Fermentation production activities in this period are based on skill, experience, mostly non-pure cultivation, and fermentation products are easily contaminated by bacteria. This is a period of natural fermentation. During this period, records of fermentation production processes also appeared in various regions of the world: In 6000 BC, the Babylonians began to use fermentation to brew beer. From 4000 BC to 3000 BC, the ancient Egyptians had mastered the fermentation method of wine, vinegar and bread, In 2000 BC the ancient Greeks and Romans use  grapes to make wines through microorganisms.
  • In 1680 Leeuwenhoek observed intact yeast cells for the first time.
  • In 1854, French chemist Pasteur discovered that the fermentation of yeast is the real cause of alcohol fermentation.
  • In 1897, German chemist Bischner discovered that the essence of carbohydrate fermentation is the various enzymes contained in yeast.
After people began to gradually understand the essence of fermentation, the history of fermented food entered the period of pure culture technology. Pure culture technology marked the transition from natural fermentation to pure culture and artificially controlled fermentation. It was the first turning point in the development of the fermentation industry. It is also the beginning of modern fermentation technology.

This has a very profound significance for the fermentation technology of bread. The yeast with strong fermentation tolerance is cultivated through the technology, and industrialized production is realized, and then through the process of drying/compression, fresh yeast , dry yeast , instant dry yeast are produced yeast and fermentation technology targeted resistance to high sugar yeast , freeze-resistant yeast , greatly improved the quality of bread products, and promote the development of the global baking industry.

The Heart of Fermentation Bioreactors/ Fermenter  : 
  • Fermentation process  is carried out in special type of vessel known as Fermenter or Bioreactor.
  • Bioreactor is defined as a vessel that carries out a biological reaction and it provide a controlled environment such as temperature, pH, substrate, salts, vitamins, oxygen etc for growth of microorganisms and product formation.
  • There are different  types of bioreactors. The major types are: Continuous Stirred Tank Bioreactors, Bubble Column Bioreactor, Airlift Bioreactors, Fluidized Bed Bioreactors, Packed Bed Bioreactors etc.
  • Fermentation tank refers to a device used for microbial fermentation in industry. Fermentation tanks are widely used in beverage, chemical, food, dairy, condiment, brewing, pharmaceutical and other industries to play a fermenting role . 
  • The components of the fermentation tank include: the tank body is mainly used for cultivating and fermenting various bacteria, with good sealing (to prevent the bacteria from being contaminated), 
  • There is a stirring slurry in the tank, which is used for continuous stirring during the fermentation process; 
  • There is aeration at the bottom 
  • The Sparger is used to pass in the air or oxygen needed for the growth of the bacteria. 
  • There are control sensors on the top plate of the tank. The most commonly used are pH electrodes and DO electrodes to monitor the changes in the pH and DO of the fermentation broth during the fermentation process.
  • The controller is used to display and control the fermentation conditions. 
  • According to the equipment of the fermentation tank, it is divided into mechanical stirring and ventilation fermentation tank and non-mechanical stirring and ventilation fermentation tank; according to the growth and metabolism of microorganisms, it is divided into aerobic fermentation tank and anaerobic fermentation tank.

Types of Fermentation

There are several types of fermentation, on the basis of Media, type of fermenter and type of end products. These fermentation types will be explained below. Check out!

  1. On the basis of Media / Substrates there are two types of fermentation solid state fermentation and Submerged fermentation. 
  2. On the basis of type of fermenter there are two types of fermentation Batch fermentation and continuous fermentation.
  3. On the  basis of end product, fermentation is of two types Aerobic fermentation and Anaerobic fermentation (Alcoholic/ethanol fermentation & Lactic acid fermentation).

On the basis of Media or Substrates
1. Solid State Fermentation
  1. Solid state fermentation (SSF) is biochemical process which involves the cultivation of microorganisms on a solid substrate with a low moisture content.
  2. In Solid state fermentation  biomolecule are manufactured which  used in the food industry, pharmaceutical industry, cosmetic products, fuel and textile industries etc.
  3. The most commonly used solid substrates in SSF are plant and animal materials, cereal grains such as Corn, rice, wheat, barley), legume seeds, straws, sawdust or wood etc.
  4. SSF fermented products mainly involves in bakery products such as bread or for the maturing of cheese. 
  5. One of the major advantage of SSF it gives higher yields and productivity, It lowers production cost, lower protein breakdown also.

2. Submerged Fermentation (SmF)
  1. Submerged fermentation (SmF) is a anaerobic process involves in inoculation of the microbial culture into the liquid medium for production biomolecules is known as Submerged fermentation. 
  2. In the submerged fermentation process, the substrate used for fermentation is always in liquid state which contains all the nutrients required for growth and development of microorganisms for production of desired products.
  3. There are four different types of submerged fermentation batch fermentation, continuous fermentation, fed batch fermentation and perfusion batch culture fermentation.
  4. Following are the examples of submerged fermentation production of citric acid, biological detergents synthesis, starch hydrolysis, cheese making, wine production.


On the basis of End Product fermentation types
1. Aerobic Fermentation
Aerobic fermentation consists of the assimilation of organic matter by microorganisms in the presence of oxygen and nutrients. Aerobic fermentation generally occurs within living organisms. Aerobic fermentation takes place in the mitochondria and the cytoplasm of cell. In Aerobic fermentation Glucose completely breaks down into oxygen and carbon dioxide.

Stages of aerobic fermentation : Aerobic fermentation is completed in three stages 
I. Glycolysis: generally occurs in the cytoplasm of living organisms and is considered the first step that involves aerobic respiration. In Glycolysis Glucose is breakdown into two pyruvate molecules. These Pyruvate molecules undergo oxidative decarboxylation to produce Acetyl-CoA. These acetyl-CoA enters in Kreb cycle. The end  products of the glycolysis is the 2 Pyruvate, 2 NADH Molecules and 2 ATP Molecules.

II. Krebs cycle : In Krebs cycle  Acetyl-CoA breakdown into carbon dioxide molecules to produce citrate, which is considered as the starting compound. The end products of the Krebs cycle are 6NADH, 2GTP, and 2FADH² . It usually takes place within the matrix of the mitochondria.

III. Electron transport chain: During oxidative phosphorylation, the formation of ATP molecules consumes the decreasing energy of NADH and FADH 2 . The electron transport chain generally occurs in the inner membrane of double-membrane mitochondria.


2. Anaerobic Fermentation :  
Anaerobic fermentation is a method that cells use to extract energy from carbohydrates in absence of oxygen. The process of anaerobic fermentation starts with glycolysis in that glucose and other sugars are oxidized to produce adenosine triphosphate (ATP) molecules that create an energy source for the cell. There are two main types of anaerobic fermentation: ethanol fermentation and lactic acid fermentation. Both restore NAD + to allow a cell to continue to generate ATP through glycolysis.

Alcoholic fermentation
Alcoholic Fermentation
Source : Wikipedia 

  1. Alcoholic fermentation is defined as it is a biochemical process in which sugar molecules is converted into alcohol and carbon dioxide with the help of yeast.
  2. Alcoholic fermentation is also known as ethanol fermentation.
  3. The main function of ethanol fermentation is to produce ATP under anaerobic conditions.
  4. This process is used for the production of alcoholic beverages, such as wine and beer, and it only happens because of the yeasts that carry out the fermentation process.
  5. Alcoholic fermentation process starts with the breakdown of sugars molecules to form pyruvate by the yeasts, which is commonly known as glycolysis.
  6. Glycolysis of a glucose molecule produces two molecules of pyruvate. Then these two molecules of pyruvate are reduced into two acetaldehyde, and this acetaldehyde is converted into two ethanol molecules and two molecules of carbon dioxide. 
  7. Duriing the alcoholic fermentation, the final electron acceptor is NAD+ and it reduced to form NADH. and these exchange of electrons results in the formation  of cellular  energy (ATP).

Lactic acid Fermentation
  1. Lactic acid fermentation is defined as it is a biochemical process in which sugar molecules is converted into lactic acid with the release of ATP Molecules by verious Bacteria Lactobacillus. 
  2. Lactobacilli are the bacteria responsible for carrying out the lactic fermentation process. These bacteria are widely used for the fermentation of milk in the production of yogurt, fermented milk and other derivatives.
  3. Lactic Acid fermentation is also known as Lacto fermentation / Lactate Fermentation.
  4. This process is used for the production of lactic acid itself and NAD+
  5. Lactic acid fermentation process starts with the breakdown of sugars molecules to form pyruvate by the Lactobacillus, which is commonly known as glycolysis.
  6. Glycolysis of a glucose molecule produces two molecules of pyruvate. Then these two molecules of pyruvate is converted into two molecules of Lactate and ATP.
  7. Duriing the Lactate fermentation, the final electron acceptor is NAD+ and it reduced to form NADH. and these exchange of electrons results in the formation of cellular energy (ATP).

Factors Affecting Fermentation Process  : 

1. Temperature
  • Temperature has many effects on the fermentation process. 
  • It will affect the rate of various enzyme reactions, change the direction of synthesis of bacterial metabolites and affect the metabolic regulation mechanism of microorganisms. 
  • In addition to these direct effects, temperature also affects the physical and chemical properties of the fermentation broth, such as the viscosity of the fermentation broth, the solubility and transfer rate of substrate and oxygen in the fermentation broth, the decomposition and absorption rate of certain substrates, etc., which in turn affect the fermentation Kinetic properties and biosynthesis of products.

2. pH
The effects of pH on the growth and reproduction of microorganisms and product synthesis are as follows:
  • Affect the activity of enzymes. When the pH value inhibits the activity of certain enzymes in the bacteria, it will hinder the metabolism of the bacteria.
  • Affect the charge state of the microbial cell membrane, change the permeability of the cell membrane, and affect the absorption of nutrients and the excretion of metabolites by the microorganisms.
  • Affect the dissociation of certain components and intermediate metabolites in the culture medium, thereby affecting the utilization of these substances by microorganisms.
  • Different pH values ​​often lead to different metabolic processes of the bacteria and change the quality and proportion of metabolites.
  • Each type of microorganism has its optimum and tolerable pH range. The optimum pH for most bacteria growth is 6.3~7.5, molds and yeasts are 3~6, ​​and actinomycetes are 7~8. Moreover, the optimum pH values ​​in the microbial growth stage and the product synthesis stage are often different, and need to be determined according to the experimental results.

3. Dissolved oxygen concentration
  • For aerobic fermentation, the dissolved oxygen concentration is one of the most important parameters. 
  • When microorganisms are cultivated in deep layers, an appropriate amount of dissolved oxygen is needed to maintain their respiratory metabolism and the synthesis of certain products. 
  • Insufficient oxygen will cause abnormal metabolism and reduce yield. 
  • The optimum oxygen concentration and critical oxygen concentration for microbial fermentation are different. 
  • The former refers to the concentration of dissolved oxygen that has the best concentration range for growth or synthesis, and the latter generally refers to the lowest oxygen concentration allowed for bacterial respiration. 
  • In order to avoid biosynthesis under oxygen-limited conditions, it is necessary to investigate the critical oxygen concentration and the maximum oxygen concentration of each fermentation process, and keep it in the range of the maximum oxygen concentration.

Advantages of Fermentation  : 
Fermentation is the process of growing microorganisms in liquid nutrient medium under suitable conditions. The products of fermentation are the cells themselves (biomass) or some of their useful products such as proteins and antibiotics. The products are obtained after a final treatment, from a process of purification with mainly biochemical techniques.
  • Fermentation process are widely used in industrial level to produce commercial products. Older applications of fermentation include the production of beer and wine with alcoholic fermentation. 
  • Fermentation process is used for the production of alcoholic beverages like beer, wine, ethanol, bread, yogurt, vinegar and kombucha and acetic acid, citric acid, gluconic acid, antibiotics, vitamins (Vitamins B12 & B2), medicines and other chemicals etc.
  • The main advantage  of fermentation is we can produce the product of interest in a large quantity with good quality, that is, to have a high yield.
  • Fermented Products contains a large amount of protein and other nutrients and is used as food by humans or animals.
  • Verious dairy products such as bread, Cultured buttermilk, Chinese, sour cream, kefir and  yogurt are produced by with the help of specific organisms, such as Lactobacillus and Streptococcus etc.
  • With the help of fermentation methane is produced by sewage water treatment with sediments of plants and freshwater.

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