Acetobacter suboxydans, or as it has been renamed, Gluconobacter oxydans, turns out to be a rather industrially useful bacteria as well as having quite an interesting history behind it. G. oxydans gets its name from oxys; Latin for "sharp, acidic", and dans; "giving". This oxidizing bacteria is Gram type-negative of the ACETOBACTERACEAE found on flowers and fruit, and can be used for sorbose fermentation, which will be discussed shortly. They are typically ovoid or rod-shaped and grow to be as large as 0.8µm x 4.2µm, and are non-motile or lophotrichously flagellated. Since they are catalase positive they are obligately aerobic organisms. The colonies are circular with a diameter of 3mm, raised or convex, and are regularly edged. They may be white in color, yellow, or even brown towards the middle of the colony. Their optimal growth temperature is 25-30oC, however, no growth occurs at 37oC. They prefer pHs of 5.5 - 6.0.
They are historically interesting because they oxidize ethanol to acetic acid, which as we know, is vinegar. Vinegar production is over 6000 years old, and in the Babylonian kitchen it would often be fermented with raisins or dates to make the drink-of-choice for those times. Later, as wine production would yield a better tasting drink with a higher alcohol content, the vinegar drinks of years past were left to be drunk by slaves, peasants, and soldiers, leaving the more prestigious wines for the home or for seasonal festivities. However, a slight bit of G. oxydans finding its way from the grape-skin into the fermenting wine was important because it could spoil the wine by producing acetic acid (acetaldehydes) which would overpower the natural aroma or bouquet. Most wines should peak around 5 to 10 years past vintage, but if G. oxydans managed to thrive for even a little bit in the anaerobic environment then that wine would be spoiled. As important as bouquet is in wine, several other notable conclusions were made regarding wine and vinegar production:
1)alcoholic fermentation and vinegar formation are two distinct processes
2)the role of oxygen in vinegar formation is important
3)the elucidation of the chemical structure of acetic acid
4)and the biological nature of vinegar productionThe regrouping of A. suboxydans to G. oxydans resulted from the discovery that the Gluconobacter genus lacks the hexose monophosphate pathway. In general, this acetification of beer and wine by G. oxydans is regarded as spoilage.
An additional note to categorization: following the publication of the 8th edition of Bergey's Manual, five subspecies of G. oxydans could be differentiated: oxydans, industrius, suboxydans, melanogenes, and sphaericus. Of the Gluconobacter genus, oxydans is the only species.
As mentioned earlier, G. oxydans is used in industry for the oxidation of sorbitol to sorbose. These two sugars are involved in L-ascorbic acid production. G. oxydans possesses sorbitol dehydrogenase which completely oxidizes D-sorbitol to L-sorbose via the Bertrand-Hudson rule: "polyols with a cis-arrangement of two secondary hydroxyl groups in D-configurations to the adjacent primary alcohol group are oxidized to the corresponding ketoses". So, in the presence of D-sorbitol, sorbitol dehydrogenase effectively oxidizes it with ~60% yield, to L-sorbose, which is then subjected to a series of reactions to ultimately yield vitamin C. Also, following the same rule, 2,3 butanediol can be converted to acetylmethylcarbinol. These are examples of how industry has utilized microbes to perform very selective reactions.
References:
1.Balows, Albert. The Prokaryotes. 2nd ed., vol 3, 1992. pp.2298-2285.
2.Bergey's Manual of Systematic Bacteriology. vol 1, 1984. pp.275-278.
3.Cummins, Joseph T. The Biological Oxidation of Sorbitol. Journal of Biological Chemistry. 1957. pp.323-330.
4.Singleton, Paul. Dictionary of Microbiology and Molecular Biology. 2nd ed. 1987. pp.4, 390.
5.Joshi, V.K. Fermentative Production of L-sorbose from D-sorbitol by Acetobacter suboxydans (Vinegar Isolate). Indian Journal of Experimental Biology. vol 12, September 1974. pp.422-424.*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
Return to Missouri S&T Microbiology HomePage Go to DJW's HomePage
This Document is maintained by djwesten@ mst.edu
