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A. Beneficial Activities of Saprobic Fungi 2. Industrial Production of Drugs |
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2. Industrial Production of Drugs a. Immunosuppressants: Cyclosporine
Fig. 4-1. Cyclosporine, for immunosuppression is critical for transplant patients. The active principle in Sandimmune* (Sandoz Labs) is a cyclopeptide immunosuppressant agent consisting of 11 amino acids. It is produced as a metabolite of the fungus Tolypocladium inflatum. Sandimmune is sold as a soft gelatin capsule or in ampules (Fig. 4-2) for injection.
Fig. 4-2. Sandimmune capsules. It is a potent immunosuppresive agent that in animals prolongs survival of allogenic transplants involving skin, heart, kidney, pancreas, lung, liver, and other organs. It must be administered with extreme care because patients may experience various side reactions and cyclosporine can interact unfavorably with many other drugs. The mode of activity is not clearly understood. Eleven species of Tolypocladium have been described (Bissett, 1983, Can. J. Bot. 61:1311-1329). Bisset determined that T. inflatum (Fig. 4-3) had an earlier valid name, T. niveum.
Fig. 4-3. Light micrograph of Tolypocladium inflatum, the fungus used in the production cyclosporine. All species are soil-inhabiting, some found infecting microscopic animals. Tolypocladium inflatum was first described by Gams (1971, Persoonia 6:185-191). An interesting discovery was made by Hodge (1995, Inoculum 46), who found that the sexual state of T. niveum is a species of Cordyceps (Fig. 4-4), one of the perithecial ascomycetes (Fig. 4-5), and a well-known entomopathogenic fungus.
Fig. 4-4. The ascomycete Cordyceps, the sexual stage of T. niveum.
Fig. 4-5. Perithecia of the ascomycete Cordyceps , the sexual stage of T. niveum. The Quarterly Newsletter of the American
Type Culture Collection (Vol. 12(1): 1-8) also lists Neocosmospora boninensis and N.
vasinfecta var. africana
as producers of cyclosporine. CellCept: More recently Syntex-Roche, of Hoffman-LaRoche Laboratories, has marketed a new immunosuppresant mycophenolate mofetil called CellCept (Fig. 4-6), a metabolite of Penicillium glaucum (Fig. 4-7) which, according to Thom & Raper (1968, A manual of Penicillia, Hafner Pub. Co., NY), is a synonym of P. expansum. This fungus is very common on rotting apples, pears, and other fruits in storage, forming a yellow-green to blue-green colony. One of my friends who received a kidney transplant a few years ago is on a combination of cyclosporine and CellCept.
Fig.4-6. CellCept, an immunosuppressant containing mycophenolate mofetil, a metabolite of Penicillium glaucum.
Fig. 4-7. Yellow-green colonies of Penicillium glaucum growing in pure culture on a nutrient agar. b. Antibiotics:
Mycotoxins are secondary metabolites that are produced by an
organism that can be toxic or inhibitory to other organisms, usually at
very low levels. Fungal mycotoxins have been shown to be very effective
against all major groups of organisms. Those of beneficial use to man have
been classified as
antibiotics.
Many of the antibiotics are especially inhibitory towards bacteria and
other organisms that are of concern in human and veterinary medicine.
Almost 150 species of fungi have been shown to produce mycotoxins; several
of these are some of our most important antibiotics (see review by Abdel
& El-Sayed. 1992. Production of penicillins and cephalosporins by
fungi, Handb. Appl. Mycol 4:517-564). Species of Aspergillus
and Penicillium, for example,
have been shown to produce close to 25 important antibiotics. Penicillin: In 1929, Alexander Fleming is credited with the discovery and naming of penicillin. He found certain colonies of Penicillium that contaminated bacterial plates would provide a large clear zone of inhibition (Fig. 4-8).
Fig. 4-8. Clear zones of inhibition surrounding small cups containing test levels of penicillin, which are paced on an agar plate inoculated with Staphylococcus. Realizing the antibiotic nature of the metabolite, he was able to grow the fungus in liquid culture and with assistance from chemists at Oxford University isolate the active property, naming it penicillin (you do note the difference in spelling?). While penicillin can be produced by a number of species of Penicillium, P. notatum and P. chrysogenum (Fig. 4-9) still remain the most effective species for producing the drug.
Fig. 4-9. Three strains of Penicillium chrysogenum used to produce penicillin. Much of the initial work on penicillin production was done at Oxford University in England. Later, however, extensive work was done at the Northern Regional Research Laboratory, a USDA lab in Peoria, IL. (NRRL) where scientists spent considerable time perfecting the techniques for the production of penicillin in submerged cultures (Raper and Thom, 1968, A manual of Penicillia, Hafner Pub. Co, NY). Research with P. chrysogenum and related strains has permitted a 1000-fold increase in the production of penicillin over that of the original strains (Fig. 4-10).
Fig. 4-10. Large fermentation tanks used for the manufacture of penicillin. Cephalosporin, a related antibiotic, and penicillin are unusual molecules due to their b-lactam ring system. Mutagens such as nitrogen mustard, UV light, nitrous acid, and X-ray have been used in attempts to develop more efficient strains. Cephalosporin is produced by Cephalosporium acremonium (Fig. 4-11) and Paecilomyces persicinus.
Fig. 4-11. Cephalosporium acremonium. CLICK HERE TO GO TO TOP OF RIGHT SIDE COLUMN
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Ancef (Smith Kline), Ceclor
(Lilly), and Cefizox (Fujisama)
are some of the common products on the market that contain cephalosporin (Fig. 4-12; Fig.
4-13).
Fig. 4-12. Ancef, one of the brand names of cephalosporin.
Fig. 4-13. Ceclor, another brand of cephalosporin. Antifungal antibiotics: Griseofulvin is an effective systemic antifungal antibiotic used in the treatment of infections of nails, hair, and skin (Fig. 4-14). It is produced by a number of species of Penicillium, including P. griseofulvum, P. aethiopicum, P. janezewski, and P. lanosus, but is commercially produced by P. patulum. Griseofulvin was 1st isolated by Oxford et al. (1939. Biochem. J. 33: 240-248) from cultures grown on media containing only glucose as its sole carbon source.
Fig. 4-14. Grifulvin V, a brand name antibiotic containing griseofulvin. There are several products available containing griseofulvin: Fulvin P/G tablets (Schering Co.) (Fig. 4-15), and Grifulvin V (Squibb), containing microcrystals of griseofulvin and are especially effective against a number of species of Tinea, Trichophyton, Epidermophyton, and Microsporium, that cause of ringworm, jocky itch, nail infections, and a number of other skin and scalp problems discussed in a later chapter.
Fig. 4-15. Fulvicin tablets, Shering's brand containing griseofulvin. There are several other antifungal antibiotics available on the market. Many of them are obtained from a fungal-like bacterial group, Streptomyces, of the Actinomycetes. Some of the common antibiotics from Actinomycetes include mycostatin and nystatin (Bristol Myers), intraveneus fungizone (Squibb), grisactin (Wyeth-Ayerst), gris-PEG (Herbert Labs), Mycelex (Miles Phar.) and amoxicillin (Smith Kline). Nystatin was the first antifungal antibiotic to be introduced for clinical use. It is produced by the Actinomycete, Streptomyces noursei, and has proven very useful in the treatment of cutaneous infections caused by Candida. Amphotericin-B, also produced by a species of Streptomyces, is the most effective antibiotic for fungi that cause systemic infections. This is especially important in problems of mucormycosis caused by various Zygomycetes and can quickly become deep-seated. Pimaricin produced S. natalensis has been recommended as an aerosol to treat pulminary Candidiasis and Aspergillosis, and as a lotion for cutaneous infections. Patulin: Raistrick et al. (1943, Lancelot 2:625-635) and Anslow et al. (1943, Soc. Chem. Ind. J. 62: 236-238) first reported the production of patulin from two species of Penicillium, P. expansum and P. patulum. The same antibiotic has been reported from other species of Penicillium and Aspergillus, going under the names claviformin and clavicin. Clavicin: Wiesner (1942, Nature 149:356-357) reported substances from culture filtrates of Aspergillus clavatus that inhibited growth of Staphylococcus aureus. In subsequent research, the active compound was identified and called clavicin. It was later shown that claviformin was also the same compound. More that 20 other antibiotics are produced by species of Penicillium (see Raper & Thom, 1968, Manual of Penicillia, Hafner Pub. Co., NY). c. Organic Acids:
The use of fungi in the production of organic acids is extensive. Close to
50 acids are produced commercially from various species of Penicillium. Several other genera, fermenting various substrates,
are utilized to produce other commercially important compounds. Fungi
produce a large number of organic acids, however, only citric acid,
gluconic acid and itaconic acid are produced in significant quantities by
large-scale commercial processes (Bigelis & Arora, 1992. Handb. Appl.
Mycology 4:357-376). Citric acid: Improved
strains of Aspergillus niger are
used in the production of citric acid in computer controlled fermentors.
More than 350,000 tons of citric acid are produced annually, and it is
used in a large variety of foods, beverages, pharmaceuticals, cosmetics,
and detergents. Gluconic acid
is produced commercially with other strains of A.
niger, in which hydrolyzed starch is used as the major substrate.
Gluconic acid is used as a cleaning agent, and in the treatment of anemia
and calcium deficiency. Itaconic acid
is produced commercially with improved strains of Aspergillus
terreus. Glucose, sucrose, and molasses have been used as substrates.
Itaconic acid is used extensively as a plasticizer to improve the adhesive
qualities of paints and in printer’s inks. d. Commercial Polysaccharides: Several polysaccharides have commercial
value or potential. Chief of these are pullulan, b-glucans, and
chitin. Pullulan is a polysaccharide produced by Aureobasidium pullulans and can be woven into fibers and has
potential in the production and strengthening of fabrics. Special fishing
lines and bulletproof vests are some of the products that contain these
special polysaccharides. Beta-glucans
produced by certain yeast are being used for encapsulation of foods and medicines. They control the slow release
of flavors and drugs. Chitin is
second behind cellulose as the most abundant compound in nature.
Commercially produced chitin in used in threads for suturing and as fillers in different foods. e. Amino Acids:
Cellular and filamentous fungi can form the amino acids commonly found in
proteins. Commercial production of amino acids is largely done by the use
of bacteria. Yet, tryptophan, lysine, and methionine have so far been only
produced by fungi (Yoshinago, 1983. Amino acids, Addison-Wesley, Reading,
MA). While bacteria are more efficient, fungi are receiving more attention
because of their ability to use more complicated substrates. Species of Hansenula,
Candida, Saccharomycopsis, Aspergillus,
and Penicillium are among the groups being studied for amino acid
production. f. Plant Growth Regulators: Chemical compounds with the capability of coordinating the growth and
morphogenesis of plants are called plant growth regulators (PGR). They
include gibberellins, cytokinins,
auxins, abscisic acid, and ethylene. Gibberellins
are the only ones produced through fungal fermentation (Lansone &
Kumar, 1992. Handb. Appl. Mycol.4: 565-607). A total of 71 gibberellins
are currently known; 25 of which are produced by fungi. Gibberellins were
first isolated from Gibberella
fujikuroi, the sexual state of Fusarium
moniliforme, when it was discovered that rice infected with this
fungus grew faster than normal. It’s importance as a plant growth
stimulator was soon recognized and more than 4 tons of gibberellins are
sold annually. Gibberella fujikuroi
and Fusarium moniliforme are
used industrially where fermentation of substrates is done in 5-6000 gal
vats. g. Generating Edible Biomass: About 155.2 billion tons of organic
matter is synthesized through photosynthesis every year (Bassham, 1975.
Biotech. Bioeng. Symp. No. 6. Intersci. Pub., NY). Much of this biomass is
inedible. Fortunately, the fungi are inheritantly able to break down most
of this inedible organic waste. Many fungi show great potential for
turning such waste into human food, fuel, or other useful compounds. Mycoprotein: a
novel food:
According to Trinci (1995. Can. J. Bot. 73 [suppl. 1]: S1-S14),
forecasters predicted a worldwide shortage of protein-rich foods by the
1980s. Research centers in England were encouraged to find ways of
converting starchy substrates into protein-rich foods. A protein-rich food
was produced from industrial fermentation by Fusarium
graminearum in which the final product could be formulated with the
proper texture, taste, and smell. Consequently, Marlow Foods helped to
develop and market mycoprotein food products under the trademark “Quorn”. Today Quorn is sold as an ingredient in over 50 types of
meals. h. Paper Made from Bracket Fungi: Polypores are very amenable to the
preparation of paper from their flesh. The resulting paper is of very high
quality and attractive in appearance. Species of
Lenzites,
Trametes , and Fomes have proven to be most useful in paper making (King
& Watling, 1997. The Mycologist 11:52-54). i. Fungi as Research Tools: Because of their small size, ease of culture and manipulation, and their
short life cycle, fungi have been great tools for various kinds of
research. Volumes could be written on how fungi are used in medical and
industrial research, but one example will give you an idea of their
effectiveness. It involves the common bakers or brewers yeast, Saccharomyces
cerevisiae. Yeast is a general term to refer to cellular fungi
that divide by budding or fission. Yeasts are used extensively in the
production of various foods and beverages. The common yeast, Saccharomyces
cerevisiae, was the first eukaryote to have its complete genome
mapped (Bussey, The Sciences, April 1996). It turns out that the yeast
cell is a “stripped down” human cell. Scientists hope to have the
human genome completely mapped by 2020. As gene mapping continues in
humans, each new gene discovered in humans has been shown to be present in
yeasts; even the gene for cystic fibrosis. The
cure for cystic fibrosis will likely come from research with this yeast. |
