Mixed acid fermentation

In <a href="/facts/Biochemistry/fa2pWEBp">biochemistry</a>, mixed acid fermentation is the <a href="/facts/Metabolism/WxDrm8k5">metabolic process</a> by which a six-carbon <a href="/facts/Carbohydrate/Geuuzxsf">sugar</a> (e.g. <a href="/facts/Glucose/oUSkoLCD">glucose</a>, C6H12O6) is converted into a complex and variable mixture of <a href="/facts/Acid/FySU18n1">acids</a>. It is an <a href="/facts/Anaerobic_organism/bhQnlqCq">anaerobic</a> (non-oxygen-requiring) <a href="/facts/Fermentation/rxaDr28b">fermentation</a> reaction that is common in <a href="/facts/Bacteria/wC8xSCsU">bacteria</a>. It is characteristic for members of the <a href="/facts/Enterobacteriaceae/6vh55fHY">Enterobacteriaceae</a>, a large family of <a href="/facts/Gram-negative_bacteria/S1PbVtp4">Gram-negative bacteria</a> that includes <a href="/facts/Escherichia_coli/nR4Gvl56">E. coli</a>.
The mixture of end products produced by mixed acid fermentation includes <a href="/facts/Lactic_acid/BsVRFx7s">lactate</a>, <a href="/facts/Acetate/U90VVczy">acetate</a>, <a href="/facts/Succinate/v3KJqrQC">succinate</a>, <a href="/facts/Formate/Py3GhI7L">formate</a>, <a href="/facts/Ethanol/3lCLfBSP">ethanol</a> and the gases H2 and CO2. The formation of these end products depends on the presence of certain key <a href="/facts/Enzyme/DSI1Fh7y">enzymes</a> in the bacterium. The proportion in which they are formed varies between different bacterial species. The mixed acid fermentation pathway differs from other fermentation pathways, which produce fewer end products in fixed amounts. The end products of mixed acid fermentation can have many useful applications in <a href="/facts/Biotechnology/8eFnI6FB">biotechnology</a> and <a href="/facts/Industrial_fermentation/k6S7gqBl">industry</a>. For instance, ethanol is widely used as a <a href="/facts/Biofuel/RWu7b6Y3">biofuel</a>. Therefore, multiple bacterial strains have been <a href="/facts/Metabolic_engineering/quTXJR6r">metabolically engineered</a> in the laboratory to increase the individual <a href="/facts/Yield_(chemistry)/fkBhd9dH">yields</a> of certain end products. This research has been carried out primarily in E. coli and is ongoing. Variations of mixed acid fermentation occur in a number of bacterial species, including bacterial <a href="/facts/Pathogen/axMXtV1M">pathogens</a> such as <a href="/facts/Haemophilus_influenzae/wqIpoDI1">Haemophilus influenzae</a> where mostly acetate and succinate are produced and lactate can serve as a growth substrate.

Mixed acid fermentation open-in-new

Mixed acid fermentation