In general what are the reagents and products of fermentation?

In fermentation glucose (sugar) is degraded into pyruvic acid (every glucose molecule forms two pyruvic acid molecules). In this method two molecules of ATP are formed.

According to the type of fermentation, pyruvic acid can make ethanol and carbon dioxide (in alcoholic fermentation) or lactic acid (in lactic fermentation). There are other varieties of fermentation in which pyruvic acid can make acetic acid (acetic fermentation), propionic acid, isopropanol (an alcohol too), etc. The type of fermentation depends on the species of the involved organisms.