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Lactic acid fermentation is a metabolic process by which glucose or other six-carbon sugars (also, disaccharides of six-carbon sugars, e.g. sucrose or lactose) are converted into cellular energy and the metabolite lactate, which is lactic acid in solution.
These lactic acid bacteria can carry out either homolactic fermentation, where the end-product is mostly lactic acid, or heterolactic fermentation, where some lactate is further metabolized to ethanol and carbon dioxide [18] (via the phosphoketolase pathway), acetate, or other metabolic products, e.g.: C 6 H 12 O 6 → CH 3 CHOHCOOH + C 2 H 5 ...
The lactic acid bacteria (LAB) are either rod-shaped (), or spherical (), and are characterized by an increased tolerance to acidity (low pH range).This aspect helps LAB to outcompete other bacteria in a natural fermentation, as they can withstand the increased acidity from organic acid production (e.g., lactic acid).
Lactic acid fermentation is relatively inefficient. The waste products lactic acid and ethanol have not been fully oxidized and still contain energy, but it requires the addition of oxygen to extract this energy. [8] Generally, lactic acid fermentation occurs only when aerobic cells are lacking oxygen.
One of the chemical processes that Pasteur studied was the fermentation of sugar into lactic acid, as occurs in the souring of milk. In an 1857 experiment, Pasteur was able to isolate microorganisms present in lactic acid ferment after the chemical process had taken place. [9] Pasteur then cultivated the microorganisms in a culture with his ...
Pathway by which glucose is converted to lactic acid as a means of energy production. L. acidophilus is a homofermentative anaerobic microorganism, meaning it only produces lactic acid as an end product of fermentation; and that it can only ferment hexoses (not pentoses) by way of the EMP pathway (glycolysis). [5]
The capability to produce lactic acid is one of the reasons why L. lactis is one of the most important microorganisms in the dairy industry. [5] Based on its history in food fermentation, L. lactis has generally recognized as safe (GRAS) status, [6] [7] with few case reports of it being an opportunistic pathogen. [8] [9] [10]
These organisms use lactic acid fermentation or mixed acid fermentation pathways to produce an ethanol end product. [3] The ethanol generated from these pathways is absorbed in the small intestine, causing an increase in blood alcohol concentrations that produce the effects of intoxication without the consumption of alcohol. [4]