An apparatus that maintains optimal conditions for the growth of microorganisms, used in large-scale fermentation and in the commercial production of antibiotics and hormones .Some commodity chemicals, such as acetic acid, citric acid, and ethanol are made by fermentation .The rate of fermentation depends on the concentration of microorganisms, cells, cellular components, and enzymes as well as temperature, pH. and for aerobic fermentation oxygen.
Fermentation has a number of commercial applications. Many occur in the food preparation and processing industry. A variety of bacteria are used in the production of olives, cucumber pickles, and sauerkraut from raw olives, cucumbers, and cabbage, respectively. Another application of the fermentation process is in the treatment of wastewater. In the activated sludge process, aerobic bacteria (bacteria that can live without oxygen) are used to ferment organic material in wastewater. Solid wastes are converted to carbon dioxide, water, and mineral salts.