Acetobacter aceti is a species of bacteria known for its ability to convert ethanol (alcohol) into acetic acid in the presence of oxygen. This conversion is a key part of the process for making vinegar, but in the context of wine, beer, or other alcoholic beverages, the activity of Acetobacter aceti is generally undesirable as it leads to spoilage.

These bacteria belong to the genus Acetobacter, which is part of the family Acetobacteraceae. They are acetic acid bacteria, characterized by their ability to oxidize ethanol to acetic acid aerobically (in the presence of oxygen). Acetobacter aceti is Gram-negative and typically found in environments where ethanol is present, including fermented foods and drinks.

In the vinegar industry, the abilities of Acetobacter aceti are harnessed under controlled conditions to produce vinegar. This is achieved by exposing alcohol to oxygen in the presence of these bacteria. The resulting acetic acid gives vinegar its distinctive sour taste and pungent smell.

However, in winemaking, brewing, and other alcoholic beverage production, the presence of Acetobacter aceti is usually prevented or minimized, as it can lead to the unwanted conversion of alcohol into acetic acid, making the product taste sour and vinegary, a fault known as acetic acid taint or vinegar taint. To prevent this, alcoholic beverages are typically stored in oxygen-limiting environments and may also be treated with sulfur dioxide to inhibit the growth of these bacteria.