d

• Ethanol fermentation


  Microbial production of ethyl alcohol from agricultural commodities for blending into gasoline to decrease dependence on imported crude oil
• Microbial conversion of agricultural substrates into ethanol is an ancient practice that predates the science of microbiology, the chemistry of the distillation process, and the engineering of an ethanol fermentation plant
• In the mid-1900s, microbial production of ethanol was replaced by synthetic ethanol derived from petroleum as the major source of this chemical
• With the recognition in the 1970s that petroleum reserves are being rapidly depleted, researchers began to update the fermentation technology for industrial ethanol production

  
• Pasteur's research with French wines in the 1860s defined the basic concepts of the fermentation process and commercial interests in beer, wine, and hard liquor production promoted continual interest in understanding the biochemistry of ethanol fermentations

  
• Efficient ethanol fermentation process

  Proper understanding of the biochemical mechanism by which ethanol is produced
• Microbes produce ethanol


  • When growth parameters do not support an oxidative metabolic process, requiring facultative microorganisms to employ a less efficient pathway which produces ethanol as a metabolic waste product
  • If air is allowed to enter the fermentation process in sufficient quantities, microbial metabolism will switch from an anaerobic, ethanol-producing process to the more efficient, aerobic process and no further ethanol will be produced

  
• Certain microorganisms are able to grow on organic compounds such as sugars in the absence of oxygen, utilizing organic compounds as electron acceptors instead of oxygen, and producing ethanol as a waste product of the fermentation process instead of water