Microorganisms fermentative fuel production

The potential use of immobilised cells in fermentation processes for fuel production has been described previously. If intact microbial cells are directly immobilised, the removal of microorganisms from downstream product can be omitted and the loss of intracellular enzyme activity can be kept to a minimum level.11... 

Microorganisms have been identified and exploited for more than a century. The Babylonians and Sumerians used yeast to prepare alcohol. There is a great history beyond fermentation processes, which explains the applications of microbial processes that resulted in the production of food and beverages. In the mid-nineteenth century, Louis Pasteur understood the role of microorganisms in fermented food, wine, alcohols, beverages, cheese, milk, yoghurt and other dairy products, fuels, and fine chemical industries. He identified many microbial processes and discovered the first principal role of fermentation, which was that microbes required substrate to produce primary and secondary metabolites, and end products. 

Biochemical conversion, or bioconversion, is a chemical reaction caused by treating moist biomass with microorganisms such as enzymes or fungi. The end products may be liquid or gaseous fuels. Anaerobic digestion and fermentation are the two processes used for biochemically... 

The product may be located inside a microorganism (intracellular) or outside in the growth medium (extracellular), or alternatively, the product could be the whole cell material. The nature of the product may be solid or dissolved in the aqueous phase. For example, the product is found in the aqueous phase for a fuel ethanol fermentation, within the cell for a therapeutic protein, while the product is the whole cell in the case of single cell protein. The location of the product influences the choice of a bioseparation method which may favor the efficient recovery of either the solid or liquid phase. The relative difficulty of separating intracellular products from other unwanted insoluble materials may influence the subsequent processing steps once the solids phase has been recovered from the fermentation broth. 

Following antibiotics production, microbial industrial fermentations have been used for the production of different metabolites endogenously produced by microorganisms, e.g., enzymes for different applications and large-scale production of bioethanol for fuel usage. 

Cell Harvesting/Washing. In recent years, the use or microorganism-based fermentations for the production of chemical products has greatly expanded. Interferon, insulin, novel antibiotics, cytotoxic antitumor agents, numerous enzymes, fine chemicals, and even fuels have been produced in carefully controlled fermentations. A key step in the fermentation cycle is the separation of the cells or cellular debris from the liquid phase of the fermentation broth-commonly called "cell harvesting". 

Spent solids ate often pressed to recover occluded liquid. The press liquor may be recycled to the leaching system as part of the vent feed, or it may be concentrated and ad(M back to the pressed solids, which are then dried to produce by-products, such as animal feed. The pressed solids may be combined with fuel and burned. If the pressing removes sufficient water, the solids can provide substantial net fuel value. In some cases spent solids can be chemically hydrolyzed or treated with microorganisms to generate fermentable sugars, single-cell proteins, or other valuable products. 

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