The metabolic function of 2,3-butanediol is not known, although some have speculated that it was an evolutionary advantage for these microorganisms to produce a neutral product that's less inhibitory than other partial oxidation products and doesn't reduce the pH as much as mixed acids. .
Comparison with mixed acid fermentation
2,3-butanediol fermentation produces smaller amounts of acid than mixed acid fermentation, and butanediol, ethanol, CO2 and H2 are the end products. While equal amounts of CO2 and H2 are created during mixed acid fermentation, butanediol fermentation produces more than twice the amount of CO2 because the gases are not produced only by formate hydrogen lyase like they are in the mixed acid fermentation
2,3 Butanediol is produced at varying levels in aerated fermentations as long as the dissolved oxygen level is limiting (i.e., the culture is trying to consume more oxygen than is available). The degree of oxygen limitation dictates the ratios of 2,3-butanediol to by-products produced (2)
- M.Madigan & J. Martinko, 11th edition, (2006) Brock's Biology of Microorganisms, NJ, Pearson Prentice Hall, (p. 351-355)
2. N. B. Jansen, M. C. Flickinger, G. T. Tsao (1984). "Production of 2,3-butanediol from D-xylose by Klebsiella oxytoca ATCC 8724." Biotechnol. Bioeng. 26 (4): 362-8.