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September 2006 Volume 4 | Issue 9

Hello hello,

I hope you had a nice summer and are enjoying the fall. What follows is an article about industrial uses of fungi by Dr. Michelle Seidl and about the fungi Epicoccum Dawn Yates. I hope you'll find them interesting and helpful.

With best wishes,
Dave Gallup




Industrial Uses of Fungi

By Dr. Michelle Seidl

Many fungi are useful to humans and have been exploited both industrially and commercially. Societies have utilized fungi for centuries in a wide variety of ways by capitalizing on the metabolism and metabolites (chemicals made from metabolism) produced. The oldest and best known example is the use of yeasts performing fermentation in brewing, wine making and bread making. Yeasts and other fungi play a critical role in drug production, food processing, bio-control agents, enzyme biotechnology, as well as research and development.

The use of yeast (e.g. Saccharomyces cerevisae) to make alcohol and carbon dioxide uses the fermentation process to break down sugars. Up to 50% of the sugar can be converted to alcohol, but rarely surpasses 15% because the fungi are sensitive to high concentrations of alcohol. In the beer making industry, cereal grains are fermented to make the final product. Wine is composed of fermented grapes while hard cider is essentially fermented apples. Sake is produced by rice fermentation, using Aspergillus oryzae and then an additional fermentation step utilizing bacteria and yeasts. With bread making, fermentation utilizes sugar to produce carbon dioxide and alcohol. The carbon dioxide produces the bubbles and causes bread to rise, while the alcohol produced evaporates off while baking. A variety of foods and drinks are fermented before consumption. Some of the largest industries in the west are based around production of alcohol and bread. In the east, the production of soy sauce and other fermented soybean products are likely among the largest industries. The peoples of Asia have developed a wide variety of interesting fermented foods, sauces and drinks, using fungi. Other examples and the applicable fungi include koji (Aspergillus); miso, soy bean paste (Aspergillus); sufu, Chinese cheese (Rhizopus), nyufu or fuyu, bean cake or bean cheese (Rhizopus); shoyu or soy sauce (Aspergillus, Saccharomyces) and tempeh (Rhizopus).

Another way in which fungi are used industrially in the food industry is in cheese production. Various cheeses are inoculated with Penicillium roquefortii to impart a strong and pungent flavor in the resultant cheeses. Examples are Roquefort, Gorgonzola, Stilton Blue and Danish Blue. The white crust on the outside of the cheeses known as Brie and Camembert is the mycelium of Penicillium camembertii. These strong flavors are a result of the fungus producing methyl ketones.

Aspergillus is utilized industrially in a number of ways. Most sodas and soft drinks contain citric acid as a main ingredient. Citric acid is also used in other drinks, many candies, canned goods, baked goods, etc. It is too expensive to isolate the citric acid from citrus fruits so it is produced in large-scale fermentation vats utilizing Aspergillus niger. Authentic soy sauce is fermented in a three-step process with the fungi Aspergillus oryzae and Zygosaccharomyces rouxii, as well as the bacterium Pediococcus halophilus (Comm. Dr. S. N. Rajagopal, Biological and Agricultural Engineering, Univ. AR).

Aspergillus sp.
Copyright © 2006 Environmental Microbiology Laboratory, Inc.

Fungi are very useful organisms in biotechnology. They are important experimental organisms easily cultured, occupy little space, multiply rapidly and have a short life cycle. Many fungi are used as model organisms for genetics, cell biology and molecular biology. The now famous "one gene one enzyme" hypothesis in the ascomycete fungus Neurospora won Beadle and Tatum the Nobel Prize. Currently there are about 1,600 antibiotics commercially produced and a number of medical drugs are manufactured using various fungi. These multi-billion dollar industries include examples such as anti-cholesterol statins, the antibiotic penicillin, the immunosuppressant cyclosporins and steroids. Statins have been used to reduce cholesterol and prevent cardiovascular disease. The group of statins derived via fermentation include: lovastatin (first isolated from Aspergillus terreus and the first statin approved by the FDA in 1987), pravastatin (isolated from Nocardia autotrophica), and mevastatin (from the fungi Hypomyces, Paecilomyces, and Trichoderma, and a fermentation product of Penicillium citrinum). Since its discovery in 1941, the antibiotic penicillin from the fungus Penicillium notatum (often called P. chrysogenum) has revolutionized human health and disease treatment. Cephalosporins are another group of antibiotics originally produced by the fungus Cephalosporium (synonym of Acremonium). First discovered as a powerful immunosuppressant in the 1970's, cyclosporins are a primary metabolite of several fungi, including Trichoderma, Tolypocladium and Cylindrocarpon. Cyclosporins have proven to be useful in mammals, being widely used during and after bone marrow and organ transplants in humans. The steroid in "the pill" is produced industrially by the fungus Rhizopus nigricans. Steroids, such as cortisone (used in arthritis treatment) and prednisone, are manufactured with the help of molds.

The only useful antifungal agent from fungi is griseofulvin. The original source was Penicillium griseofulvin. Griseofulvin is fungistatic (inhibits fungal growth), rather than fungicidal (destroys fungi). It is used for the treatment of dermatophytes, as it accumulates in the hair and skin following topical application. These antifungal agents are readily and cheaply produced industrially.

Penicillium sp.
Copyright © 2006 Environmental Microbiology Laboratory, Inc.

Ergot alkaloids have a number of medicinal uses, the most widespread being migraine treatment. The vasodilator activity reduces tension during an attack. These alkaloids are now produced industrially in culture using strains of Claviceps.

A number of industrial applications use the biological activity of fungi involved in the alteration of plant cell walls. Fungi are able to break down plant cell walls by the production of a wide variety of enzymes. Enzymes are used to treat and modify fibers, particularly during textile processing and in caring for textiles afterwards. For example, enzymes called catalases are used to treat cotton fibers and prepare them for the dyeing processes. By degrading surface fibers, many enzymes, including some cellulases and xylanases, are used to finish fabrics, help in the tanning of leathers or give jeans a stonewashed effect. Stonewashed jeans are placed in a large vat containing the fungus Trichoderma, which produces enzymes (cellulases) that partially digest the cotton fibers of the jeans to add softness and produce the stonewashed look. The natural enzyme supplement Beano™, contains the enzyme (α-galacatosidase) from Aspergillus terreus, used for digestive discomfort. The pulp and paper industry benefits from the enzyme production capabilities of certain fungi to soften wood fibers and provide alternatives to chemical bleaching. For example, the basidiomycetes Trametes and Phanerochaete are used for lignin biodegradation and Bjerkandera is used for hardwood cellulose bio-bleaching by producing the enzymes peroxidase and xylanase. Certain fungi are the primary source for xylanases, which are used industrially to breakdown xylan, the second most abundant polysaccharide in nature.

Enzymes are a sustainable alternative to the use of harsh chemicals in industry. Because enzymes work under moderate conditions, such as warm temperatures and neutral pH, they reduce energy consumption by eliminating the need to maintain extreme environments, as required by many chemically catalyzed reactions. Reducing energy consumption leads to decreased greenhouse gas emissions. Enzymes also reduce water consumption and chemical waste production during manufacturing processes. Because enzymes react to specific situations and minimize the production of by-products, they offer minimal risk to humans, wildlife, and the environment. Enzymes are both economically and environmentally beneficial because they are safely inactivated and create little or no waste; rather than being discarded, end-product enzymatic material may be treated and used as fertilizer. Enzyme research using fungi has been very active and promising in recent years. For example the enzyme laccase produced from different fungi was used to make paper. This process led to a 30% reduction in energy consumption, a 50% reduction in chemical product usage and a greater resistance to tearing.

Enzymes are also used to make food more edible or desirable by removing, adding or modifying components such as vitamins, nutritional elements, colors and flavors. Fungi are a common contributor to the processing of foods. Certain fungi produce a range of compounds that alter the color of food. For instance, Monoascus purpureus has been traditionally used for the production of red wine. The pigments are polyketides that are insoluble in acid conditions. A range of zygomycete fungi in the Mucorales produces beta-carotene, commonly added to a variety of foods. A recent concern with the potentially toxic or allergic reactions of some artificial coloring agents has led to a closer examination of colors from these natural sources. Used in animal nutrition and food enrichment, the biocatalytic production of vitamin B2 (riboflavin) replaced chemical synthesis in the early 1990's. It is now commonly produced by fermentation of the ascomycete fungus Ashbya gossypii. Since large quantities of enzymes are often needed for industrial usage, fermentation vats fulfill this need.

Fungal food items are also produced on an industrial scale. For instance, edible mushrooms are grown on large-scale farms. These delicious and nutritious natural products have seen a large increase during the past few decades. Many contain a protein profile that rivals that of beans and most contain large amounts of B vitamins and minerals. Another food product example is Quorn™, the brand name of an all-natural, meat-free frozen food. Quorn™ brand has been sold in the UK since 1985. In 2002 it was launched in the U.S. and has since become the best-selling frozen meat-free brand in natural food stores. It can be found in various meat-like forms such as patties, (veggie) dogs, roasts, and tenders (similar to chicken nuggets). This efficient and nutritious protein source consists of a mycoprotein from the fungus Fusarium venenatum.

In the various fields of agriculture, medicine, environmental biology, biotechnology, research and development; fungi provide novel and important products and applications. Their extraordinary usefulness has provided us with numerous advantageous products and will undoubtedly afford us with additional medicines, foodstuffs, enzymes, amenities and other valuable items in the future.

CORRECTION: The original September 2006 issue of Environmental Reporter misstated the enzyme responsible for the active ingredient in Beano™. The correct enzyme is alpha-galactosidase.

References:
1. Alexopoulos, C.J., C.W. Mims, M. Blackwell. 1996. Introductory Mycology. John Wiley & Sons, USA.

2. Beg, Q.K., M. Kapoor, L. Mahajan, G.S. Hoondal. 2004. Microbial xylanases and their industrial applications: a review. Appl. Microbiol. and Biotech. Springer Berlin/Heidelberg.

3. Gow N. & Gadd G.M. (Eds)(1995) The Growing Fungus. Chapman Hall, London.

4. http://www.TomVolkFungi.net

5. History of Fermented Tofu

6. Wainwright M. (1995) An Introduction to Fungal Biotechnology. Wiley, Chichester.

7. The Biodiversity of Filamentous Fungi

8. Quorn™ website




Fungus of the Month: Epicoccum
By Dawne Yates

Epicoccum (phonetic: Epp-ee-cock-um) is a very common fungus that is an early secondary invader on all sorts of plants, particularly damaged plant tissue, and is often found on leaf spots with other fungi. It has been isolated from air, moldy paper, plant materials, animals, insects, foodstuffs, textiles, soil, and occasionally occurs in house dust. It is mostly saprophytic (obtaining food from dead or decaying organic matter), or weakly parasitic. It is ubiquitous in nature (found everywhere) and is commonly found in outdoor air. It is known to be very resistant to changes in water activity; having been known to resume growth after long periods of drying.

 

Figure 1: Drawings of Epicoccum
Copyright © 2006 Environmental Microbiology Laboratory, Inc.

Spores are produced very quickly and our MoldRange™ data shows the highest recovery rate, of about 30% to 35%, in the summer and the lowest recovery rate, of about 10% to 15%, in the winter. See Figure 2 below.

Figure 2: Frequency of detection and spore density by month for Epicoccum.
The gray bars represent the frequency of detection, from 0 to 1 (1=100%), graphed against the left axis. The red, green, and purple lines represent the 2.5, 50, and 97.5 percentile airborne spore densities, when recovered, graphed against the right hand axis. (Source: EMLab™ MoldRange data. Total sample size for this graph: 39,878.)

Morphology:
In culture, Epicoccum is fast growing on general fungal media, and produces colonies which are woolly and/or downy in appearance. Colony colors include yellow, orange, red or brown. As the colony ages they usually become darker and black dots (spores growing on colonies) may be observed on the colony surface. These are tufts of hyphae that are cushion-shaped, non-convoluted and are called sporodochium (a cushion-like mass of conidiophores, conidia and conidiogenous cells produced above the substrate).

When observed on spore trap samples, immature Epicoccum spores may look round, non-septate, and may be pale in color, whereas when they are mature, can appear rough, warty-looking and brown to black in color, with both transverse and oblique septa, which makes them resemble a soccer ball. The broad attachment area at the base is often visible. Mature spores are most commonly 15-25 µm in diameter, but are also seen smaller and much larger (up to 50 µm diameter). Intact spores are distinctive, however young immature spores may be confused with Ulocladium, Stemphylium or possibly Alternaria. On a tape lift, Epicoccum is easily distinguishable providing the growth is mature enough to include the conidiophores and conidia.

Figure 3: Single Epicoccum spore in air sample.
Copyright © 2006 Environmental Microbiology Laboratory, Inc.

Health Effects:
Epicoccum has been known to cause Type 1 allergies (hay fever and asthma). Rarely, it can cause infections in the skin due to its ability to grow at 37°C.

References:
1. Barron, G.L. "The Genera of Hyphomycetes From Soil"

2. Ellis, M.B. "Dematiaceous Hyphomycetes"

3. Watanabe, T. "Pictorial Atlas of Soil and Seed Fungi"



The data and other information contained in this newsletter are provided for informational purposes only and should not be relied upon for any other purpose. Environmental Microbiology Laboratory, Inc. hereby disclaims any liability for any and all direct, indirect, punitive, incidental, special or consequential damages arising out of the use or interpretation of the data or other information contained in, or any actions taken or omitted in reliance upon, this newsletter. Images included in this newsletter are property of Environmental Microbiology Laboratory, Inc., unless otherwise specified.