Mycoderma aceti

Acetous fermentation [souring) is caused by Mycoderma aceti, which consists of oval cells with a marked constriction in the middle, resemblance to the figure 8 being thus produced. The cells are considerably smaller (about 10 times) than those of M. vini. In some cases several individuals are joined in a chain. 

If you leave a bottle of wine (which contains alcohol) opened and exposed to the air, it will, after a while, start to smell (and taste) of sour apples. Leave it a little while longer and it will start to smell (and taste) of vinegar. This is because the wine contains ethanol (a primary alcohol) which reacts with and is oxidised by the oxygen in the air (shown as [O]) in the presence of micro-organisms such as Mycoderma aceti, as shown in Figure 7.1.7. 

Derivation (1) Bacterial fermentation of apple cider, wine, or other fruit juice. (2) Fermentation of malt or barley. The fermenting agent is usually a mold, e.g., Mycoderma aceti, generally known as mother. Either type can be distilled to remove color and other impurities and is then called white vinegar. 

The true ferments are therefore all organized beings, such as torula cerenisice, producing alcoholic fermentation glaucum, producing lactic acid fermentation and mycoderma aceti, producing acetic acid fermentation. 

Pasteur was the first to include flor with bacterial problems, because, like acetic spoilage, it involves a mycodermic microorganism. However, flor is caused by a yeast (which Pasteur called My coderma vini) and not a bacterium (Mycoderma aceti). Flor should not be confused with the bloom formed by Saccharomyces cerevisiae under certain, specific, conditions, responsible for producing high-quality wines such as Sherry and Vin Jaune from the Jura (Volume 1, Section 14.5). 

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