Utilization of ethanol by acetic acid bacteria.

It is well known that the acetic acid bacteria can rapidly oxidize ethanol to acetic acid. But whether ethanol can serve as a source of carbon and energy for these bacteria has not been clearly established. Pasteur (1868) noted that Mycoderma aceti which is undoubtedly Acetobacter aceti (Frateur, 1950) can grow well in ethanol media only if acetic acid is also present. Addition of one or two per cent acetic acid was required for growth in an ethanol yeast water medium and also in a chemically defined medium consisting of ethanol, mineral salts, and ammonium nitrogen. Both Hoyer (1898) and Beijerinck (1898) confirmed Pasteur's results and showed that A. aceti cannot grow in an ethanol-mineral salts-ammonium nitrogen medium unless acetic acid, acetate, or glucose is added. Growth with ethanol alone occurred when tap water was used in place of distilled water, and this was explained by Beijerinck as due to the organic impurities in tap water which stimulated growth. These results can be interpreted in several ways. It may be that the ethanol is not used for carbon and energy and that these functions are served by the acetic acid or other organic compounds that must be added to ethanol containing media to permit growth. Or the acetic acid or other compounds may stimulate the utilization of ethanol for carbon and energy but are not themselves so used. This seems quite unlikely. Or both ethanol and acetic acid may be the sources of carbon and energy. The fact that tap water may stimulate growth of A. aceti with ethanol seems to indicate that under such conditions the ethanol functions as the primary source of energy for growth since it seems unlikely that the organic impurities in tap water would be sufficient for that purpose. The situation with respect to ethanol utilization