Industrial Microorganisms and Product Formation Industrial Microorganisms and Their Products
Industrial microbiology uses microorganisms, typically grown on a large scale, to produce valuable commercial products or to carry out important chemical transformations. The actual reactions carried out by microorganisms in industrial microbiology are called biocatalysis (Figure 30.1).
An industrial microorganism must produce the product of interest in high yield; grow rapidly on inexpensive culture media available in bulk quantities; be amenable to genetic manipulation; and, if possible, be nonpathogenic. There are many industrial products, including both cells and substances made by cells. Commodity chemicals are inexpensive chemicals produced in bulk, including ethanol, citric acid, and many others.
Primary and Secondary Metabolites Primary metabolites are produced during active cell growth, and secondary metabolites are produced near the onset of stationary phase (Figure 30.2).
Table 30.1 shows fermentor sizes for various industrial processes.
Fermentation Scale-Up Fermentation scale-up is the process of gradually converting a useful industrial fermentation from laboratory scale to production scale. Aeration is a particularly critical aspect to monitor during scale-up studies.
Major Industrial Products for the Health Industry Antibiotics: Isolation and Characterization
The industrial production of antibiotics begins with screening for antibiotic producers (Figure 30.7).
Cephalosporins are valued clinically not only because of their low toxicity but also because they are broad-spectrum antibiotics, useful against a wide variety of bacterial pathogens.
Figure 30.10 shows the kinetics of the penicillin fermentation with Penicillium chrysogenum.
If the penicillin fermentation is carried out without addition of side-chain precursors, the natural penicillins are produced. The fermentation can be more directed by adding to the broth a side-chain precursor so that only one desired penicillin is produced.
The product formed under these conditions is referred to as a biosynthetic penicillin. To produce the most useful penicillins, those with activity against gram-negative Bacteria, a combined fermentation and chemical approach is used that leads to the production of semisynthetic penicillins. All of these antibiotics are typical secondary metabolites, and their industrial production is well worked out despite the fact that the biochemistry and genetics of their biosynthesis are only partially understood.
Vitamins and Amino Acids Vitamins produced microbially include vitamin B 12 and riboflavin (Figure 30.12).
Enzymes as Industrial Products Microorganisms are ideal for the large-scale production of enzymes. Many enzymes are used in the laundry industry to remove stains from clothing, and thermostable and alkalistable enzymes have many advantages in these markets.
Certain enzymes are produced in large amounts by some organisms, and instead of being held within the cell, they are excreted into the medium. These extracellular enzymes, called exoenzymes, can digest insoluble polymers such as cellulose, protein, and starch. The products of digestion are then transported into the cell where they are used as nutrients for growth.
The term extremozyme has been coined to describe enzymes that function at some environmental extreme, such as high temperatures or low pH (Figure 30.15). Enzymes from extremophiles are desirable for biocatalyses under extreme conditions.
Table 30.4 lists microbial enzymes and their applications.
Major Industrial Products for the Food and Beverage Industries Alcohol and Alcoholic Beverages
Alcoholic beverages are produced by yeast from the fermentation of sugar to ethyl alcohol and CO 2.Wine is produced from grape juice (Figure 30.18), beer from fermentation of malted grain (brewing), and distilled beverages from the distillation of fermented solutions.
Adequate aeration is the most important consideration in ensuring a successful vinegar process.
Figure 30.23 is a diagram of a vinegar generator.
Citric Acid and Other Organic Compounds A number of organic chemicals are produced commercially by use of microorganisms, of which the most important economically is citric acid, produced by Aspergillus niger (Figure 30.24).