Introduction
Fermentation is a type of anaerobic respiration . It is an energy releasing, catabolic, enzymatic stepwise incomplete breakdown of food without employing oxygen. It is a less efficient mode of respiration as it produces little amount of energy. Its end products contain at least one organic component which can be further oxidised on getting O2. Since no oxygen is used, therefore, H2O is not produced as an end product.Katychev coined the term anaerobic respiration. Pfluger called it intramolecular respiration. Anaerobic respiration by microorganisms or their enzymes outside the cell in a liquid medium is usually called fermentation.Fermentation is a type of anaerobic, incomplete breakdown of organic food carried out primarily by fungi and bacteria or their enzymes in liquid medium. It is independent of presence or absence of oxygen but is more rapid in the absence of oxygen. Gay Lussac was the first to give a reaction for the fermentation of sugar. The only energy extraction mechanism in fermentation is glycolysis
Anaerobic Respiration Exercising Alcohol fermentation, also known as ethanol fermentation, happens when single-celled organisms convert pyruvate to ethanol while also generating carbon dioxide. This method is used to make bread, wine, beer and ethanol fuels.
Fermentation Types
Depending on the number of end products, there are two forms of fermentation.
Homo Fermentation – This kind produces only one end product.
Hetero Fermentation – This kind produces many end products.
After fermentation, numerous end products are generated, and fermentation is classified into distinct categories based on the type of end product formed:
Fermentation of Lactic Acid
Lactic acid fermentation converts glucose and other six-carbon carbohydrates into the metabolite lactate and cellular energy. When there is insufficient oxygen supply to allow aerobic respiration to continue, anaerobic fermentation occurs most commonly in bacteria, some animal cells, mammalian red blood cells and occasionally in skeletal muscles. Lactic acid is formed from pyruvate generated during glycolysis in this procedure. Lactate dehydrogenase catalyses the process that produces NAD+ from NADH. During exercise, the lactic acid produced by anaerobic respiration accumulates in the cell, causing weariness.
Fermentation of Alcohol
Because ethanol is the end product of alcohol fermentation, it is also known as ethanol fermentation. The conversion of simple carbohydrates to carbon dioxide and ethanol is mostly carried out by yeast. It is commonly used in the wine, beer, and biofuel sectors, among other things. The carbon dioxide is released as pyruvic acid is broken down into acetaldehyde. Ethanol is produced from acetaldehyde. NADH generates NAD+, which is then used in glycolysis. Both phases of the process are catalysed by enzymes. Pyruvic acid decarboxylase and alcohol dehydrogenase are the enzymes that break down pyruvic acid.
Fermentation of Acetic Acid
The fermentation of acetic acid is the method used to make vinegar. The steps in the two-step method are as follows:
Using yeast, anaerobically produce ethyl alcohol from sugar.
Using acetobacter and aerobic respiration, ethyl alcohol is converted to acetic acid.
Fermentation of Butyric acid
Butyric acid fermentation : It occurs in butter by acid bacteria (Bacillus butyricus and Clostridium butyricum) and makes it sour and foul smell. These bacteria convert hexose sugar and lactic acid into butyric acid.
Cellular respiration under anaerobic conditions
Anaerobic cellular respiration is similar to aerobic cellular respiration in that electrons are taken from a fuel molecule and then transmitted via an electron transport chain to drive ATP production. Sulphate is used by certain species as the last electron acceptor at the conclusion of the electron transport chain, whereas others use nitrate. Some prokaryotes, such as bacteria and archaea, use anaerobic respiration in low-oxygen settings to break down fuels. Methanogens, for example, may employ carbon dioxide as a terminal electron acceptor and produce methane as a byproduct.
Anaerobic Respiration – Fermentation
Fermentation is a kind of heterotrophic metabolism in which the terminal electron acceptor is organic carbon rather than oxygen. This implies that these organisms do not employ an electron transport chain to convert NADH to NAD+. Therefore, they must find another way to utilise this reducing power and keep a supply of NAD+ available for typical metabolic pathways to work properly (e.g. glycolysis ). Fermentative organisms are anaerobic, as they do not require oxygen. When anaerobic circumstances exist, many species can employ fermentation, but they can use aerobic respiration when oxygen is present. These creatures are facultative anaerobes, which means that they can survive without oxygen. Obligately fermentative organisms typically lack a complete citric acid cycle to avoid excessive NADH generation. ATP is created in fermentative organisms through substrate-level phosphorylation, which involves transferring a phosphate group from a high-energy organic chemical to ADP to make ATP instead of employing an ATP synthase as in respiration. Fermentative organisms utilise NADH and other cofactors to create a variety of reduced metabolic by-products, including hydrogen gas, to build high energy phosphate-containing organic molecules (usually in the form of CoA-esters) (H2). The result of glycolysis, small organic acids and alcohols generated from pyruvate are the most common reduced organic molecules. Ethanol, acetate, lactate, and butyrate are among the examples. Fermentative organisms are particularly essential in the food industry and are used to create a variety of goods. Each meal’s diverse flavours and qualities are due to the different metabolic end products generated by each distinct bacterium species.
Conclusion
Anaerobic fermentation is a metabolic process that converts carbohydrates (sugar) into organic acids, gases, or alcohols in anaerobic circumstances. It is found in all bacteria and eukaryotes. As a result, microorganisms are employed to manufacture nutraceuticals or bacteriocins by accumulating a variety of primary and secondary metabolites. Anaerobic fermentation has a wide range of uses. It might be used to make ethanol, butyl alcohol, lactic acid, acetic acid, hydrogen gas, and various nutraceutical and antibacterial compounds with medicinal or health benefits.