As the diagram at the right indicates, all that is obtained from the conversion of glucose to lactate is two molecules of ATP, which makes anaerobic glycolysis a very inefficient process. Yeasts in wine can get nineteen times as much energy per mole of glucose by oxidizing it all the way to C0₂ and H₂0, than by fermenting it anaerobically to ethanol. The winemaker uses this fact to encourage rapid growth of the yeast culture early in the wine-making process by bubbling air through the crushed grapes. No ethanol is produced under these circumstances, but the yeasts multiply rapidly in the presence of a large energy supply. After the yeast colony is large, aeration is halted and the grape juice in the vat is covered with a layer of carbon dioxide to keep out oxygen. The yeasts stop multiplying, turn off their citric acid cycle, and settle down to the anaerobic conversion of glucose to ethanol - less rewarding for the yeast, but more rewarding for the winemaker.

Bacteria have a much richer chemistry. All bacteria begin with fermentation, and for some this is the end of the process. They degrade glucose (and a few other molecules) anaerobically to a number of different waste products; ethanol, or lactic, formic, acetic, propionic, or butyric acids. Other bacteria respire using 0₂, giving off H₂0 as eucaryotes do. Still others can use sulfate or nitrate as their oxidizing agents. Oxidation with nitrate (yielding N₂) appears to be a recent special adaptation in some bacteria that always prefer 0₂ if available. But sulfate respiration (yielding H₂S) may be an independent and very old line of metabolic evolution.