Bacteria, acetic acid

5 Acetic acid bacteria development in grape must 189 

6 Evolution of acetic acid bacteria during winemaking and wine aging, 

Acetic acid bacteria are very prevalent in nature and are well adapted to growth in sugar-rich and alcohol-rich environments. Wine, beer and cider are natural habitats of these bacteria when production and storage conditions are not correctly controlled. Their quality is clearly lowered, except in the case of certain very particular beers. 

Acetic acid bacteria cells generally have an ellipsoidal or rod-like form, with dimensions of 0.6-0.8 p,m by 1-4 p,m. They can be either single or organized in pairs or small chains. Some 

The cellnlar structure of an acetic bacterium is similar to that of other bacteria a cytoplasm containing genetic material (chromosome, plasmids), ribosomes and all of the enzymatic equipment, a plasmic membrane and cell wall. At the structural 

As seen in Table 2-1, acetic acid bacteria are separated from LAB by both Gram stain and catalase activity. Although generally indicative of aerobic organisms (see discussion in Procedure 2.3.2), catalase activity among some strains of Acetobacter is variable and occasionally difficult to demonstrate. 

Brewing Microbiology. http //dx.doi.org/10.1016/B97g-l-7g242-331-7.00008-3 Copyright 2015 Elsevier Ltd. All rights reserved. 

Bacteria Occurrence in brewery environments Off-flavour/ aroma and odour Visual spoilage effects Metabolic products 

Acetobacter Wort, beer dispenses, and cask-conditioned ales and barrel-aged ales, brewery biofilm Sour, vinegary Hazy, ropiness Acetic acid 

Glucano- bacter Wort, beer dispense and cask-conditioned ales Sour, vinegary Hazy Acetic acid, acetate 

Zymomonas Primed beers (not Fruity, rotten Hazy, Acetaldehyde and 

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Yamada, Y. Aida, K. Uemura,T. Distribution of ubiquinone 10 and 9 in acetic acid bacteria and its relation to the classification of genera Gluconobacter and Aceto-bacter, especially of so-called intermediate strains. Agric. Biol. Chem. 1968, 32, 786-788. 

Acetic acid Various acetic acid bacteria... 

Simple organic molecules Ethanol Butanol Acetone Acetic acid Lactic acid Saccharomyces cerevisiae Pachysolen tamiophilus, some Clostridium spp. Clostridium acetobutylicum, C. saccharoacetobutylicum Clostridium acetobutylicum, C. saccharoacetobutylicum Various acetic acid bacteria Lactobacillus spp. 

The strong oxidative capabilities of acetic acid bacteria are also harnessed for the production of other flavour acids from their corresponding alcohols, such as propanoic acid, butanoic acid, 2-methylpropanoic acid, 2-methylbutanoic acid and 3-methylbutanoic acid (Scheme 23.1). 

Scheme 23.1 a Short-chain flavour acid production from natural alcohols by acetic acid bacteria b Jasmonic acid and methyl jasmonate production with Diploida gossypina... 

Acetic acid is a weak carboxylic acid with a pungent odor that exists as a liquid at room temperature. It was probably the first acid to be produced in large quantities. The name acetic comes from acetum, which is the Latin word for sour and relates to the fact that acetic acid is responsible for the bitter taste of fermented juices. Acetic acid is produced naturally and synthetically in large quantities for industrial purposes. It forms when ubiquitous bacteria of the genera Acetobacter and Clostridium convert alcohols and sugars to acetic acid. Acetobacter, especially Acetobacter aceti, are more efficient acetic acid bacteria and produce much higher concentrations of acetic acid compared to Clostridium. 

Only a few types of microorganisms are able to survive and proliferate under the relatively high alcohol and low pH conditions which characterize most wines. Of these, yeast, acetic acid bacteria, and lactic acid bacteria are the most common. No pathogenic organisms are able to survive in wine. 

Sewage wastes contain as much as 4 ppm of vitamin Bi2 (Hoover et al. 1952B Miner and Wolnak 1953). Although frowned on for aesthetic reasons as a source of vitamin Bi2 for human nutrition, wastes from activated sludge processes may well provide the cheapest source for preparation of vitamin Bi2 concentrates used in cattle feed. Symbiotic growth of lactic and acetic acid bacteria has been recommended for producing sour milk products biologically enriched with vitamin Bi2 (Rykshina 1961). Acetic acid bacteria cultured in whey fortified with cobalt salts led to an 80-fold increase in vitamin B12. Propionic acid bacteria in skim milk supplemented with dimethylbenzimidazole increased the vitamin content by 300-fold. 

Attempts to improve the quality of whey include those of Johnstone and Pfeffer (1959), who increased its nitrogen content with a nitrogenfixing strain of E. aerogenes, and Davidov and Rykshina (1961), who used whey fortified with CoCl2, fermented it with acetic acid bacteria, and observed an 80-fold increase in vitamin B[2. 

One of the largest groups of strictly aerobic heterotrophic bacteria, the pseudomonads (Pseudomonas and related genera), are of interest to biochemists because of their ability to oxidize organic compounds, such as alkanes, aromatic hydrocarbons, and steroids, which are not attacked by most other bacteria. Often, the number of oxidative reactions used by any one species of bacteria is limited. For example, the acetic acid bacteria that live in wine and beer obtain all of their energy by oxidation of ethanol to acetic acid ... 

During mead fermentation, several problems are generally encountered. For example, the anticipated alcohol content may not be achieved within the time desired. There may also be a lack of uniformity in the final product, due to differences in water content of the honey used. In some situations, such as worts with high sugar contents, successive addition of honey is needed to avoid premature termination of fermentation. This likelihood of stuck fermentation is increased as most mead is made empirically, without adjustments. This can lead to subsequent yeast refermentation and secondary fermentations by lactic and acetic acid bacteria. These can undesirably increase acidity and the production of volatile esters (Casellas, 2005). The presence of these compounds alters... 

The artificial induction of noble rot would greatly facilitate making botrytized sweet wine, extending their production to countries where conditions are unfavorable for the natural development of noble rot. Experiments have long been performed to this end. In the earliest work, Nelson and Amerine (1956) unsuccessfully tried to induce its development in the vineyard by inoculation. The necessary moisture condition after inoculation was impossible to reproduce under field conditions. In addition, the method creates the risk that other fungi (Penicillium, Aspergillus, Rhizopus), yeasts and, acetic acid bacteria could develop if unfavorable weather conditions arose (Dittrich, 1977). 

The ability of 40 strains of acetic acid bacteria isolated from grape must and wine to produce biogenic amines was screened in synthetic medium and wine (Landete et al. 2007b), but no positive results were obtained. No further mention regarding the formation of biogenic amines by acetic acid bacteria was found in the literature. 

The acetic acid bacteria are introduced either as mother of vinegar or as a liquid culture. Small producers often use mother of vinegar. This consists of acetic acid bacteria and slime bacteria. The latter are responsible for the consistency of the mother of vinegar. They also produce metabolites, however, and for this reason acetic fermentation by mother of vinegar is not always completely pure in tone. 

The production of acetic acid from alcohol is carried out by two naturally occurring groups of acetic acid bacteria ... 

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