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A field concerned with the development of technologies to control and manipulate the growth and activities of selected biological agents to create desirable products and economic gain or to prevent economic loss. In addition to bacteria and yeasts, animal and plant cell cultures are now used to produce sophisticated products such as monoclonal antibodies, immunomodulating compounds, and complex plant metabolites.
Although fermented products have been consumed for thousands of years, only in the nineteenth century was microbial activity associated with the fermentation process. Soon after that discovery, microorganisms, especially bacteria, were selectively introduced on the commercial level. Techniques were developed gradually for pure-culture fermentation and strain improvement, but the major advance in industrial microbiology occurred during World War II with the large-scale production of penicillin by submerged-culture fermentation. In the 1950s, industrial microbiology shifted its focus to the production of therapeutic agents, especially antibiotics. Advances in molecular biology have greatly increased the potential applications of industrial microbiology in areas such as therapeutics, diagnostics, environmental protection, and agriculture. The techniques of genetic engineering, along with technology developments in bioprocessing, make possible large-scale production of complex natural compounds that would otherwise be very difficult to obtain.
With the exception of the food industry, few commercial fermentation processes use wild strains of microorganisms. Of the many thousands of microbial species, few are used commercially, and fewer still are used as hosts for genetically engineering genes. Process development occurs in large part by strain improvement directed at increasing product yield, enhancing growth on cheaper substrates, and simplifying purification.
Strain development is achieved by either a traditional mutation and selection program or direct genetic manipulation. The recombinant DNA approach has succeeded in introducing new genetic material into a convenient host microorganism and amplifying genetic material. About 20% of the synthesizing capacity of a bacterium can be devoted to a single polypeptide or protein. See Recombination (genetics)
Commercial microbial compounds are produced in two distinct phases: fermentation and product recovery. Production usually occurs in a batch fermentor, where gas of controlled composition and flow is bubbled through a stirred pure microbial culture suspended in a liquid medium of optimum nutrient composition. Product recovery and purification involves a series of operations. The first steps usually involve cell disruption or the separation of the cell or cellular debris from the fluid medium, typically through centrifugation and filtration. Later stages of purification include finer membrane filtration, extraction, precipitation, and chromatography. See Fermentation, Sterilization
The production of certain foods and beverages was an early application of industrial microbiology. Now, the fields of mineral recovery, medicine, environmental protection, and food and agriculture are using similar techniques.
Bacterial leaching reactions have been used to alter metal-bearing minerals, usually converting them to more soluble forms before the metals are extracted. Such operations can result in improved extraction rates in comparison to those of conventional processes, which are usually conducted on ore waste dumps and heaps. Large-scale commercial applications of biochemical mining and extraction have been limited mainly to copper and uranium. Besides enhancing or inhibiting the recovery of metal values from ores, bacteria are being used to precipitate or accumulate metal. The process, known as bioaccumulation, normally involves the adsorption of metal ions on the bacteria, which are then chemically transformed to an insoluble precipitate.
The most visible products of industrial microbiology are therapeutics for human health. Microbial synthesis is the preferred method of production for most health care drugs with complex chemistry. Microorganisms still have a remarkable ability for producing new commercial antibiotics, the largest class of drugs, and for continued yield improvement. With recombinant DNA technology, many proteins and polypeptides that are present naturally in the human body in trace amounts can be produced in large amounts during fermentation of recombinant microorganisms. See Antibiotic, Insulin
Microbial activities have long been the basis for sewage treatment facilities, and industrial and hazardous waste cleanup, or bioremediation, has become important. Bioremediation successes have been achieved by using native bacteria to degrade petroleum products, toxic chlorinated herbicides, and toxic biocides. See Hazardous waste, Sewage
Some of the oldest and most established areas of industrial microbiology concern food and beverage products, such as the production and use of brewer's yeast and baker's yeast. The food industry and the detergent industry are the major users of industrial enzymes produced by microbial fermentation. Detergents, especially in Europe, often contain protein-degrading enzymes (proteases). In the food industry, amylases convert starch to glucose, and glucose isomerase converts glucose to fructose.