Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistryit is narrowly defined as the extraction of energy from carbohydrates in the absence of respiration. In the context of food productionit may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. In microorganisms, fermentation is the primary means of producing adenosine triphosphate ATP by the degradation of organic nutrients anaerobically.
For example, fermentation is used for preservation in a process that produces lactic acid found in such sour foods as pickled cucumberskombuchakimchiand yogurtas well as for producing alcoholic beverages such as wine and beer.
Fermentation also occurs within the gastrointestinal tracts of all animals, including humans. Below are some definitions of fermentation. They range from informal, general usages to more scientific definitions.
What Are the Two Main Types of Fermentation?
Along with photosynthesis and aerobic respirationfermentation is a way of extracting energy from molecules, but it is the only one common to all bacteria and eukaryotes.
It is therefore considered the oldest metabolic pathwaysuitable for an environment that does not yet have oxygen. The basic mechanism for fermentation remains present in all cells of higher organisms. Mammalian muscle carries out the fermentation that occurs during periods of intense exercise where oxygen supply becomes limited, resulting in the creation of lactic acid.
Fermentative bacteria play an essential role in the production of methane in habitats ranging from the rumens of cattle to sewage digesters and freshwater sediments. They produce hydrogen, carbon dioxide, formate and acetate and carboxylic acids ; and then consortia of microbes convert the carbon dioxide and acetate to methane. Acetogenic bacteria oxidize the acids, obtaining more acetate and either hydrogen or formate.
Finally, methanogens which are in the domain Archea convert acetate to methane. Fermentation reacts NADH with an endogenousorganic electron acceptor. However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Fermentation products contain chemical energy they are not fully oxidizedbut are considered waste products, since they cannot be metabolized further without the use of oxygen.
Fermentation normally occurs in an anaerobic environment. This is called oxidative phosphorylationand it generates much more ATP than glycolysis alone.The following points highlight the eight main types of fermentations.
Two Types of Fermentation (Plus Fun Facts)
The types are:- 1. Batch Fermentation 2. Continuous Fermentation 3. Fed Batch Fermentation 4. Anaerobic Fermentation 5. Aerobic Fermentation 6. Surface Fermentations 7. Submerged Fermentations 8. State Fermentation. A batch fermentation is a closed culture system, because initial and limited amount of sterilized nutrient medium is introduced into the fermenter. The medium is inoculated with a suitable microorganism and incubated for a definite period for fermentation to proceed under optimal physiological conditions.
Oxygen in the form of air, an antifoam agent and acid or base, to control the pH, are being added during the course of fermentation process Fig. During the course of incubation, the cells of the microorganism undergo multiplication and pass through different phases of growth and metabolism due to which there will be change in the composition of culture medium, the biomass and metabolites.
The fermentation is run for a definite period or until the nutrients are exhausted. The culture broth is harvested and the product is separated.Fermentation Frenzy - 4 Different Fermented Products
Batch fermentation may be used to produce biomass, primary metabolites and secondary metabolites under cultural conditions supporting the fastest growth rate and maximum growth would be used for biomass production.
The exponential phase of growth should be prolonged to get optimum yield of primary metabolite, while it should be reduced to get optimum yield of secondary metabolites.
The used medium along with cells of microorganism and the product is drawn out from the fermenter. When the desired product is formed in optimum quantities, the product is separated from the microorganism and purified later on. It has both advantages and disadvantages which are detailed below:.
It is a closed system of fermentation, run for indefinite period. In this method, fresh nutrient medium is added continuously or intermittently to the fermenter and equivalent amount of used medium with microorganisms is withdrawn continuously or intermittently for the recovery of cells or fermentation products Fig. As a result, volume of the medium and concentration of nutrients at optimum level are being maintained.
This has been operated in an automatic manner. The continuous fermenter has its maximum use that take long time to reach high productivity, reduces down time and lowers the operating costs. In continuous mode, starting medium and inoculum are added to the fermenter. After the culture is grown the fermenter is fed with nutrients and broth is withdrawn at the same rate maintaining a constant volume of broth in the fermenter.Fermented food is packed with nutritional value, including vitamins and minerals, good bacteria, and live enzymes.
Lactic acid fermentation refers to a biological process whereby glucose and other six-carbon sugars are converted into the metabolite lactate and into cellular energy.
Six-carbon sugars include sugars such as lactose and sucrose. Lactic acid fermentation is an anaerobic fermentation reaction occurring in some bacteria and some animal cells, including the cells of the muscles. Lactic acid bacteria are important when it comes to producing and preserving wholesome foods. Lactic acid fermentation is generally inexpensive, and it often requires no heat in its preparation, which means they are also fuel-efficient.
If foods are fermented with lactic acid, they play a vital role in feeding the population of the world, from continent to continent. Lactic acid bacteria perform an important function in that they preserve and produce dozens of foodsincluding:. Both lactic acid fermentation and brining are popular for processing and preserving vegetables because they are inexpensive and have low energy requirements for both functions, and they result in many versatile flavors.
The salt concentration can affect the course of the fermentation, which in turn affects the softening and prevents putrefaction. There are other advantages, of course, including making foods resistant to spoilage and the development of toxins.
When it comes to providing inexpensive and nutritious foods to the hungry people of the world, one of the best methods of food preservation and processing is the lactic acid fermentation process, and this goes for all foods, including milk-cereal mixtures and even fresh vegetables. Afterward, this is used in glycolysis. A good example of the process is the soreness you feel after you play a hard game of basketball or football.
Lactic acid builds up in the muscles as you exercise, which is why you feel the soreness. Put another way, in this process glucose, sucrose, and fructose convert into cellular energy and into lactate, which is a metabolite. When it comes to lactic acid fermentation, even your muscle cells can be affected. In the fermentation process, the production of ATP is minus oxygen, as the process is done only through glycolysis. Glycolysis breaks down a glucose molecule into two pyruvate molecules, and this results in a net gain of two NADH molecules and two ATP.
When you work your muscles too hard, the buildup of lactic acid causes pain and sometimes inflammation. When you work out, your cardiovascular and respiratory systems are unable to transport oxygen to your muscle cells, especially the muscle cells in your legs, quickly enough to maintain aerobic respiration. Because it must allow continuous production of some ATP, this is when your muscle cells use the lactic acid fermentation process.
Alcohol fermentation is also called ethanol fermentation, and it refers to a biological process that converts sugars such as fructose, sucrose, and glucose into cellular energy. It produces carbon dioxide and ethanol as a side effect.
The process is considered an anaerobic process because yeasts perform this conversion without oxygen. Yeast is a eukaryotic microorganism which metabolizes sugars anaerobically via a pathway called alcohol fermentation.
During this process, simple sugars are converted into carbon dioxide and ethanol. Yeasts usually function under aerobic conditions but can also function anaerobically. In alcohol fermentation, yeast starts with glucose, which is a kind of sugar but ends with ethanol and carbon dioxide. There are two basic parts of alcohol fermentation. The first part involves the yeast breaking down glucose in order to form two pyruvate molecules, a process known as glycolysis.
The second part involves the two pyruvate molecules being converted into two ethanol molecules and two carbon dioxide molecules. Ethanol is another word for alcohol, and this second part is called fermentation.
The main reason for alcohol fermentation is so that ATP, which is the energy currency for cells, is produced, and it is produced under anaerobic conditions. One of the reasons alcohol fermentation is so important is that it provides energy when there is an insufficient amount of oxygen present.The fermentation method used by animals and certain bacteria, like those in yogurt, is lactic acid fermentation Figure 1.
This type of fermentation is used routinely in mammalian red blood cells and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue that is, in muscles used to the point of fatigue. In muscles, lactic acid accumulation must be removed by the blood circulation and the lactate brought to the liver for further metabolism. The chemical reactions of lactic acid fermentation are the following:.
The enzyme used in this reaction is lactate dehydrogenase LDH. The reaction can proceed in either direction, but the reaction from left to right is inhibited by acidic conditions. Such lactic acid accumulation was once believed to cause muscle stiffness, fatigue, and soreness, although more recent research disputes this hypothesis.
Once the lactic acid has been removed from the muscle and circulated to the liver, it can be reconverted into pyruvic acid and further catabolized for energy. Figure 1. Lactic acid fermentation is common in muscle cells that have run out of oxygen. Tremetol, a metabolic poison found in the white snake root plant, prevents the metabolism of lactate.
When cows eat this plant, it is concentrated in the milk they produce.
Fermentation Types: 8 Types of Fermentations| Industrial Biotechnology
Humans who consume the milk become ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?
Figure 2. Fermentation of grape juice into wine produces CO 2 as a byproduct. Fermentation tanks have valves so that the pressure inside the tanks created by the carbon dioxide produced can be released. There are two main reactions in alcohol fermentation. The first reaction is catalyzed by pyruvate decarboxylase, a cytoplasmic enzyme, with a coenzyme of thiamine pyrophosphate TPP, derived from vitamin B1 and also called thiamine. A carboxyl group is removed from pyruvic acid, releasing carbon dioxide as a gas.
The loss of carbon dioxide reduces the size of the molecule by one carbon, making acetaldehyde. The fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages.
Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions. Other fermentation methods occur in bacteria. Many prokaryotes are facultatively anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of oxygen.
Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them on exposure. It should be noted that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria.
Without these pathways, that step would not occur and no ATP would be harvested from the breakdown of glucose.There are three types of fermentation processes and they are. Batch fermentation is carried out in batches. Head space plays an important role as some area of a fermentor is required for collection of air, gases, and foam which is produced during the fermentation process. Further, after inoculation of media the fermentor is steam sterilized and after sterilization, the nutrient media is cooled and inoculated with desired volume of inoculums under aseptic condition.
Fermentation process is carried out under optimum growth condition. It is stopped after specific period of time and the fermented media or broth are removed from the fermentor and the desired product is obtained. The product obtained is passed through recovery and purification process.
Later, the fermentor is cleaned and reused for the next batch. In this process, as the fermentation proceeds, the quantity of nutrients from the media gets depleted, and microbes and products increase.
In batch fermentation, growth of micro-organism is slower down due to decrease of nutrients. It requires less space, there are fewer chances of contamination and this process is easy to handle. The disadvantage is that it is a time consuming process and it requires more time for cleaning, sterilization, cooling.
The yield of the product is also low. In continous fermentation process fermentation runs continuously without emptying of fermentation tank. It involves continous addition of fresh media and withdrawal of fermentation product is constant. Each and every cell in fermentation media should be in log phase and not in stationary phase. The rate of addition of media should satisfy nutrient requirement of fermentation organism if rate of addition of media is slow there are chances that cells enter in stationary phase.
There are three types of continuous fermentation processes. In Single stage Continuous Fermentation, the fermentor is used continuously. In this process, media is added at a specific rate as well as the product formed is removed at the same rate.
The input of media and output of fermented media is balanced. In Single stage Recycle Continuous Fermentation, a single fermentor is used continuously. The rate of inoculation of fermentation media and the rate of withdrawal of fermented broth is same. In this process, a portion of fermented broth plus withdrawal culture is recycled to the fermentor.
In Multi-stage Continuous Fermentation process, two or more fermentors are operated continuously in sequence. In this fermentation process first fermentor is used for growth of cells because in some fermentation process the product is formed after cell multiplication. Here effluent of first fermentor acts as in-fluent for next fermentor.
The continuous fermentation techniques are operated by two operating systems that are chemostsat and turbidostat.The following points highlight the five main types of fermentation.
The types are: 1. Alcoholic Fermentation 2. Lactic Acid Fermentation 3. Propionic Acid Fermentation 4. Butyric Acid — Butanol Fermentation 5. Mixed Acid Fermentation. Commonly yeasts, particularly Saccharomyces cerevisiae, are used for production of various alcoholic beverages, as well as industrial alcohol. Yeasts are essentially aerobic organisms, but they can also grow as facultative anaerobes.
The energy-yield under anaerobic conditions is much lower and hence the growth is slower with much lower cell-yield. When grown with aeration, the cell-yield increases dramatically, but alcohol production falls. Thus, oxygen inhibits fermentation. This is known as Pasteur-effect. Conversion of pyruvic acid to ethanol proceeds in two steps: pyruvic acid to acetaldehyde and acetaldehyde to ethanol. The first step is catalysed by pyruvic acid decarboxylase which requires TPP as coenzyme, and the second step by alcohol dehydrogenase which requires NADH 2 as coenzyme.
Various strains of yeasts, mostly belonging to Saccharomyces cerevisiae, have been developed and carefully selected for large-scale manufacture of alcohol for different purposes.
Also, various materials and conditions are used depending on the nature of the product desired. Extract of malted partly germinated barley serves as substrate for beer production. The starting material contains large amount of maltose a dissacharide of two glucose units produced by hydrolysis of starch present in barley seeds. Maltose is split into glucose and serves as substrate for alcohol fermentation under anaerobic conditions.
Similarly, for production of wine, grape juice is the substrate of choice. Specific selected strains are employed to impart characteristic flavour and taste of different alcoholic beverages.
For manufacture of industrial alcohol, generally molasses is used as the starting material. Also sulfite liquor, which is a waste product of paper industry, is used as a cheap substrate for industrial alcohol production.
Besides yeasts, some bacteria can also carry out alcoholic fermentation. A well-known example is Zymomonas mobilis. This organism dissimilates glucose by EDP producing pyruvic acid which is converted to ethanol by decarboxylation and dehydrogenation as in yeast.The two main types of fermentation are alcoholic and lactic.
In alcoholic fermentation molecules are converted into ethanol with the production of carbon dioxide, whereas in lactic fermentation, molecules are converted into lactic acid, and there is no production of carbon dioxide. Alcoholic or ethanol fermentation is the process in which the sugars glucose, fructose and sucrose in food is converted to energy.
Bread, certain teas Kombucha and alcoholic beverages including beer, wine, whiskey, vodka and rum are produced using this method. Lactic fermentation is a similar process in which sugars are converted to energy. Lactic fermentation, however, can be more widely used when preserving foods. Fermented foods can have great benefits on health and wellness. The bacteria produced during the fermentation process, also known as probiotics, may be beneficial to digestive function and immunity.
Preserving foods via fermentation can increase their nutritional value because it makes them easier to digest and ups their vitamin levels. Fermenting foods at home has grown in popularity and is easy to achieve. A single head of cabbage, for example, can be turned into sauerkraut simply be shredding it, salting it, placing it in a jar or crock and letting it sit in the dark for about a month. Home Science. What Is the Main Function of Enzymes?