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Wednesday, July 16, 2008


Microbial fermentation is the enzymatic decomposition and utilization of foodstuffs, particularly carbohydrates, by microbes. It has always been an important part of our lives: foods can be spoiled by microbial fermentations, foods can be made by microbial fermentations, and muscle cells use fermentation to provide us with quick responses. Fermentation is often defined as a process where cells produce energy anaerobically, or without oxygen. In general, it involves the breaking down of complex organic substances into simpler ones. Microbial or animal cells obtain energy through glycolysis, splitting a sugar molecule, and removing electrons in the process. The electrons are then passed to an organic molecule such as pyruvic acid. This results in the formation of waste products that are excreted from the cell.
Microbial fermentation is any large-scale cultivation of microbes or other single cells, occurring with or without air. In the teaching lab or at the research bench, fermentation is often demonstrated in a test tube, flask, or bottle-in volumes from a few milliliters to two liters. At the production and manufacturing level, large vessels called fermenters or bioreactors are used. A bioreactor may hold several liters to several thousand liters. Bioreactors are equipped with aeration devices as well as stirrers, and pH and temperature controls. In order to get a product from fermentation, fermentation scientists develop media and test growth conditions. Then, a scale-up must be done to reproduce the process at a large volume. During production, technicians monitor temperature, pH, and growth in the bioreactors to ensure that conditions are optimum for cell growth and product. Bioreactors are used to make products such as insulin and human growth hormone from genetically engineered microorganisms as well as products from naturally-occurring cells, such as the food additive xanthan.
For one, they don't use toxic reagents or require the addition of intermediate reagents. Microbiologists are now looking for naturally occurring microbes that produce desired chemicals. In addition, they are now capable of engineering microbes to enhance production of these chemicals. In recent years, microbial fermentations have been revolutionized by the application of genetically-engineered organisms. Many fermentations use bacteria but a growing number involve culturing mammalian cells.