Fermentation

Fermentation is a metabolic process where organisms use an alternative to oxygen as a final electron acceptor in order to gain energy. Often the same molecule from which high energy electrons were harvested ultimately accepts the lower energy electron in a different molecular configuration, an example is the fermentation of glucose to ethanol. Fermentation by microorganisms has been mastered by humans for millennia, first for food preservation and more modernly as a source of chemicals.

OSE context

Fermentation is a process that must be conducted free from air and atmospheric oxygen, and can be conducted either submerged in water (liquid state) or in a seal container. Depending upon the starting material and the sugars it contains and the product desired a variety of microorganisms can be selected.

Food preservation

Fermentation will be used to preserve different food sources for longer term storage. Fermentation acts to preserve food by converting universal energy source sugars to fermentation products which cannot be used by all microorganisms. Secondly the fermentation products create an environment that is not conducive to other microorganisms, mainly by lowering the pH. The human gut flora contains many of the same microorganisms used in fermentative food preservation and consumption of fermented foods can have a high impact in improving digestive health and function.

Examples

• Cheese
• Yogurt
• Kefir
• Sauerkraut
• Kimchi
• Kombucha
• Beer
• Silage for livestock

Sauerkraut juice as starter

Sauerkraut juice is especially rich in lactofermenting organisms. It can therefore be used as a starter for other lactofermentative processes.

Chemical Engineering

Fermentation products include small organic molecules with chemical functional groups that are useful for chemical engineering. Fermentation for chemical production has been commercialized and showed promise in the early 1900s before the refinement of the petrochemical industry.

Examples:

• Ethanol
• Butanol
• Acetone
• Lactic acid

Related Wiki Pages

http://opensourceecology.org/wiki/Silage http://opensourceecology.org/wiki/Acetone-butanol-ethanol_fermentation