Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 232

Bioprocess

A bioprocess is any process that uses complete living cells or organisms or their components (e.g., bacteria, enzymes) to effect desired a physical change and/or a chemical change in the feedstock. Transport of energy and mass is fundamental to many biological and environmental processes.

Modern bioprocess technology used this principle and is actually an extension of older methods for developing useful products by taking advantage of natural biological activities. Although more sophisticated, modern bioprocess technology is based on the same principle: combining living matter (whole organisms or enzymes) with nutrients under the conditions necessary to make the desired end product. Bioprocesses have become widely used in several fields of commercial biotechnology, such as production of enzymes (used, for example, in food processing and waste management) and antibiotics.

Since bioprocesses use living material, they offer several advantages over conventional chemical methods of production. Bioprocesses usually require lower temperature, pressure, and pH (the measure of acidity) and can use renewable resources (biomass) as raw materials. In addition, greater quantities can be produced with less energy consumption.

In most bioprocesses, enzymes are used to catalyze the biochemical reactions of whole microorganisms or their cellular components. The biological catalyst causes the reactions to occur but is not changed. After a series of such reactions (which take place in large vessels (fermenters or fermentation tanks), the initial raw materials are chemically changed to form the desired end product. Nevertheless, there are challenges to the use of bioprocesses in the production of synthetic fuels.

First, the conditions under which the reactions occur must be rigidly maintained. Temperature, pressure, pH, oxygen content, and flow rate are some of the process parameters that must be kept at specific levels. With the development of automated and computerized equipment, it is becoming much easier to accurately monitor reaction conditions and thus increase production efficiency.

Second, the reactions can result in the formation of many unwanted by-products. The presence of contaminating waste material often poses a two-fold problem related to (i) the means to recover (or separate) the end product in a way that leaves as little residue as possible in the catalytic system, and (ii) the means by which the desired product can be isolated in pure form.