Acetic acid bacteria
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Acetic acid bacteria (AAB) are a group of Gram-negative bacteria which oxidize sugars or ethanol and produce acetic acid during fermentation.<ref name=Raspor2008>Template:Cite journal</ref> The acetic acid bacteria consist of 10 genera in the family Acetobacteraceae.<ref name=Raspor2008/> Several species of acetic acid bacteria are used in industry for production of certain foods and chemicals.<ref name=Raspor2008/>
DescriptionEdit
All acetic acid bacteria are rod-shaped and obligate aerobes.<ref name=Raspor2008/> Acetic acid bacteria are airborne and are ubiquitous in nature. They are actively present in environments where ethanol is being formed as a product of the fermentation of sugars. They can be isolated from the nectar of flowers and from damaged fruit. Other good sources are fresh apple cider and unpasteurized beer that has not been filter sterilized. In these liquids, they grow as a surface film due to their aerobic nature and active motility. Fruit flies or vinegar eels are considered common vectors in the propagation of acetic acid bacteria.<ref>Template:Cite book</ref>
The growth of Acetobacter in wine can be suppressed through effective sanitation, by complete exclusion of air from wine in storage, and by the use of moderate amounts of sulfur dioxide in the wine as a preservative.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
MetabolismEdit
Vinegar is produced when acetic acid bacteria act on alcoholic beverages such as wine. Specific oxidation reactions occur through oxidative fermentation, which creates vinegar as a byproduct. In the biotechnological industry, these bacteria's oxidation mechanism is exploited to produce a number of compounds such as l-ascorbic acid, dihydroxyacetone, gluconic acid, and cellulose.<ref name="Mamlouk, D. 2013">Mamlouk, D. & Gullo, M. Acetic Acid Bacteria: Physiology and Carbon Sources Oxidation. Indian Journal of Microbiology 53, 377–384 (2013).</ref> Besides food industry, some acetic acid bacteria are used as biocatalysts for the industrial production of compounds. They are used as the important biocatalysts for the development of eco-friendly fermentation processes as an alternative to the chemical synthesis.<ref name="Mamlouk, D. 2013" /> Some genera, such as Acetobacter, can oxidize ethanol to carbon dioxide and water using Krebs cycle enzymes. Other genera, such as Gluconobacter, do not oxidize ethanol, as they do not have a full set of Krebs cycle enzymes. As these bacteria produce acid, they are usually acid-tolerant, growing well below pH 5.0, although the pH optimum for growth is 5.4-6.3. Acetobacter xylinum is able to synthesize cellulose,<ref>Template:Cite journal</ref> something normally done only by plants.
ReferencesEdit
Further readingEdit
- Ecological occurrence of Gluconacetobacter diazotrophicus and nitrogen-fixing Acetobacteraceae members: their possible role in plant growth promotion 2008. Microb Ecol. 55(1):130-40.
- Genera and species in acetic acid bacteria, 2008 Int. J. Food Microbiol. Volume 125, Issue 1, Pages 15–24.
- Polyphasic taxonomy of acetic acid bacteria: An overview of the currently applied methodology, 2008 Int. J. Food Microbiol. Volume 125, Issue 1, Pages 2–14
- Biotechnological applications of acetic acid bacteria, 2008, Critical Reviews in Biotechnology, Volume 28, Issue 2, 101-124
- Evaluation of viability and growth of Acetobacter senegalensis under different stress conditions, 2013 Int. J. Food Microbiol.Volume 163, issue 2-3, 204-213