Acetobacter aceti

In fermentation for the production of acetic acid, ethyl alcohol is used in an aerobic process. In an ethanol oxidation process, the biocatalyst Acetobacter aceti was used to convert ethanol to acetic acid under aerobic conditions. A continuous fermentation for vinegar production was proposed for utilisation of non-viable A. aceti immobilised on the surface of alginate beads. 

Sun, Y., and Furusaki, S., Continuous Production of Acetic Acid Using Immobilized Acetobacter aceti in a Three-Phase Fluidized Bed Bioreactor, J. Ferm. Bioeng., 69 102 (1990)... 

Human use of acids and bases dates back thousands of years. Probably the first acid to be produced in large quantities was acetic acid, HC HjO. Vinegar is a diluted aqueous solution of acetic acid. This acid is an organic acid that forms when naturally occurring bacteria called acetobacter aceti convert alcohol to acetic acid. Ancient Sumerians used wine to produce vinegar for... 

Immobilisation of an Acetobacter aceti strain in calcium alginate resulted in improvement of the operational stability, substrate tolerance and specific activity of the cells and 23 g phenylacetic acid was produced within 9 days of fed-batch cultivation in an airlift bioreactor [133]. Lyophilised mycelia of Aspergillus oryzae and Rhizopus oryzae have been shown to efficiently catalyse ester formation with phenylacetic acid and phenylpropanoic acid and different short-chain alkanols in organic solvent media owing to their carboxylesterase activities [134, 135] (Scheme 23.8). For instance, in n-heptane with 35 mM acid and 70 mM alcohol, the formation of ethyl acetate and propylphenyl acetate was less effective (60 and 65% conversion yield) than if alcohols with increased chain lengths were used (1-butanol 85%, 3-methyl-l-butanol 86%, 1-pentanol 91%, 1-hexanol 100%). This effect was explained by a higher chemical affinity of the longer-chain alcohols, which are more hydrophobic, to the solvent. 

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. 

Acetobacter aceti Clostridium thermoaceticum Propionibacterium shermanii Aspergillus niger Yarrowia lipolytica... 

Cozier, G. E., Giles, I. G., and Anthony, C. (1995b). The structure of the quinoprotein alcohol dehydrogenase of Acetobacter aceti modelled on that of methanol dehydrogenase from Methylobacterium extorquens. Biochem. J., 308, 375—379. 

Recombinant strains of Acetobacter aceti, cloned with either alcohol dehydrogenase or aldehyde dehydrogenase, have been tested for vinegar production. The bacteria with the aldehyde dehydrogenase gene produced acetic acid more rapidly than those with the alcohol dehydrogenase, and were more resistant to high concentrations of acetic acid. 

The sequences of citrate synthases from the eukaryotes pig heart and kidney, Arabidopsis thaliana and Saccharomyces cerevisiae, and from the eubacteria Escherichia coli, Rickettsia prowazekii, Acinetobacter anitratum, Acetobacter aceti and Pseudomonas aeruginosa have been determined (see the literature [85,88] for references). In addition, a high-resolution X-ray crystallographic structure is available for the pig heart enzyme [89,90]. This has allowed the identification of 12 residues which are critical for substrate binding and catalysis multiple sequence alignments [91] have indicated that the majority of these 12 active site residues are conserved between all eukaryotic and eubacterial citrate synthases. 

Acetic acid Various sugars Acetobacter aceti Clostridium thermoaceticum Pachysolen tannophilus... 

Aat n GACGT C GACGTC CTGCAG C + TGCAG Acetobacter aceti... 

Saeki, A. (1990). Studies on acetic acid fermentation. Ill continuous production of vinegar with immobilized Saccaromycodes ludwigii cells and immobilized Acetobacter aceti cells entrapped in calcium alginate gel beads. J. Jpn. Soc. Food Sci. 37, 722-725. 

For larger scales, shallow trays made of corrosion-resistant metal or plastic placed in portable trolleys may be used for efficient liquid-air contact. The trolleys are placed in a sterile room with frequent sterile air changes under closely controlled temperature and humidity conditions. Efficient air-liquid contact may also be obtained from a loosely packed, moist, solid medium permeated with air. For instance bran is used as the substrate for enzyme production by Aspergillus oryzal. Wine vinegar (acetic acid) is produced by trickling wine (basically ethanol in water) over a short tower of wood chips, which are used both as a support and to provide air to Acetobacter aceti [13] (Eq. 16.15). By law, the acetic acid (3-5% in water) in vinegar must be produced by fermentation, and not by petrochemical methods. 

Several other organic acids are also made commercially on a large scale by microbial techniques. Some of the better known examples of these are acetic acid (vinegar) via the metabolism of alcohol in water by Acetobacter aceti, and lactic acid (Eq. 16.33), produced by Streptococcus lactis fermentation of hexose sugars. 

Matsushita, K., Inoue, T., Adachi, O., and Toyama, H. 2005. Acetobacter aceti possesses a proton motive force-dependent efflux system for acetic acid. Journal of Bacteriology 187 4346-4352. 

Nakano, S., Fukaya, M., and Horinouchi, S. 2006. Putative ABC transporter responsible for acetic acid resistance in Acetobacter aceti. Applied and Environmental Microbiology 72 497-505. 

Matsushita K, Shinagawa E, Adachi O, Ameyama M (1982) o-Type cytochrome oxidase in the membrane of aerobically grown Pseudomonas aeruginosa. FEBS Lett 139 285-288 Matsushita K, Shinagawa E, Adachi O, Ameyama M (1990) Cytochrome a1 of Acetobacter aceti is a cytochrome ba functioning as ubiquinol oxidase. Proc Natl Acad Sci USA 87 9863-9867... 

Aliphatic alcohols can be oxidized to the corresponding carboxylic acid with Acetobacter aceti as long as the amount of substrate is kept below the inhibiting level.162 The Baeyer-Villiger reaction of cyclic ketones can be carried out with monooxygenases from P. putida (9.13) or A. calcoaceticus, the former being preferred, because the latter is pathogenic.163... 

When the alcohol in wine changes into vinegar, there are two processes involved. The first one is relatively minor. Ethanol, the alcohol of beverages, reacts with oxygen to form acetic acid, a dilute solution of which we refer to as vinegar. This happens only to a very small extent, because the wine doesn t come into contact with much oxygen. What really causes wine to turn to vinegar is contamination with a bacteria called Acetobacter aceti. 

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