Fermentation is the main source of ethanol in the production of ethanol fuel. Common crops such as sugar cane, potato, cassava and corn are fermented by yeast to produce ethanol which is further processed to become fuel.

Aerobic fermentation occurs in the presence of oxygen. It usually occurs at the beginning of the fermentation process. Aerobic fermentation is usually a shorter and more intense process than anaerobic fermentation.

Fermentation does not require oxygen and is therefore anaerobic. Fermentation will replenish NAD+ from the NADH + H+ produced in glycolysis. One type of fermentation is alcohol fermentation. First, pyruvate is decarboxylated (CO2 leaves) to form acetaldehyde.

Lactic acid fermentation is the type of anaerobic respiration carried out by yogurt bacteria (Lactobacillus and others) and by your own muscle cells when you work them hard and fast.

There are two types of fermentation, alcoholic and lactic acid. Fermentation follows glycolysis in the absence of oxygen. Alcoholic fermentation produces ethanol, carbon dioxide, and NAD+. Lactic acid fermentation produces lactic acid (lactate) and NAD+.

The main fermentation products include organic acids, ethyl alcohol and carbon dioxide. Commercially the mostly important are lactic acid and ethanolic fermentations.

Regardless of the type of yeast you use, if your water reaches temperatures of 120°F or more, the yeast will begin to die off. Once water temps reach 140°F or higher, that is the point where the yeast will be completely killed off.

If the airlock is not bubbling, it may be due to a poor seal between the lid and the bucket or leaks around the grommet. Fermentation may be taking place but the CO2 is not coming out through the airlock. This can also be caused by adding too much water to the airlock.