Many steps are involved in this transformation, and the yeast must produce several different enzymes. The necessary enzymes are produced by bacteria rather than by yeast. Lactic acid is weaker than malic acid, so malolactic fermentation reduces the overall acidity of the wine. In addition, some byproducts produced during the ML fermentation can make a positive contribution to the complexity of the wine. Depending upon the winemaking conditions, several other fermentations can and often do occur in wine.
Some bacteria can ferment the glycerol in the wine into lactic and acetic acids.
The natural grape sugars can be transformed into lactic and acetic acid by other types of bacteria. A few species of bacteria can ferment the tartaric acid in the wine into lactic acid, acetic acid and carbon dioxide gas. Vinegar bacteria can convert the alcohol into acetic acid. Then the same bacteria convert the acetic acid into water and carbon dioxide gas. These other transformations can produce several materials that detract from wine quality.