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There are basically two (2) forms of fungi. These fungal forms are yeasts and moulds.


Moulds are common contaminants of household appliances, furniture, clothing’s and food. Moulds are generally saprophytic in nature and thus derive their energy and nutrient from the organic matter on which they are growing. Common mould genera that are of industrial importance include: Acremonium, Rhizopus, Fusarium, Penicillium, Mucor, Aspergillus, and Cladosporium. Moulds grow on dead organic matter and they can become visible to the naked eyes especially when they form large colonies. They thrive at various temperature conditions and can even survive some harsh conditions in the environment. Moulds are spoilage organisms even though some species of mould such as Penicillium species are of immense industrial importance because of the metabolites that they produce. Moulds cause disease in humans and animals. They are important spoilage organisms of food and raw materials for food production.

The importance of moulds is as follows:

  1. Moulds secrete hydrolytic enzymes that can degrade high molecular weight materials or biopolymers such as starch, lignin and cellulose into simpler substances. This ability can be exploited to produce enzymes or substances that can be used to degrade biological wastes in the environment.
  2. They play important roles in the production of various foods and beverages.
  3. Moulds are important in the production of some antibiotics such as penicillin sourced from Penicillium chrysogenum and P. notatum.
  4. Moulds are important in most fermentation process involved in wine production, food and other beverages production.
  5. Citric acid for soft drink production and some enzymes for bread making are from moulds. For example, Aspergillus niger is a mould that is used in industries for mass production of citric acid.
  6. Citric acid from Aspergillus niger is used to produce numerous products ranging from household cleaners, pharmaceuticals, foods, cosmetics, photography and construction.
  7. Aspergillus species is also commonly used in large-scale fermentation in the production of alcoholic beverages.


Saccharomyces cerevisiae  is a species of yeast that is also called the baker’s yeast. It is one of the most useful yeast species because it has been used in baking and brewing since ancient times. Yeasts are common in the environment and are isolated from sugar-rich materials such as palm wine and food products high in carbohydrates. Brewer’s yeast, ale yeast, top fermenting yeast, baker’s yeast and budding yeast are other names that S. cerevisiae is known for. These names connotes to the different applications of the yeast in the production of a wide variety of economically useful products. S. cerevisiae can grow aerobically on simple carbohydrate sources such as glucose, and maltose. They use ammonia and urea as their sole nitrogen source. Yeasts also require phosphorous and some minerals for their optimal growth.

The importance of yeast is as follows:

  1. Yeasts are used in brewing beer.
  2. They are used in baking bread.
  3. Yeasts are used in wine fermentation.
  4. They are used for the industrial production of ethanol and other industrial fuels.
  5. Yeasts such as S. boulardii are used in the production of probiotics used to maintain the health of the gastrointestinal tract.
  6. Yeasts convert sugars to carbon dioxide (CO2) and ethanol; and can be used to generate CO2 to nourish plants in aquariums.
  7. Yeasts also cause food spoilage.

Further reading

Anaissie E.J, McGinnis M.R, Pfaller M.A (2009). Clinical Mycology. 2nd ed. Philadelphia, PA: Churchill Livingstone Elsevier. London.

Baumgardner D.J (2012). Soil-related bacterial and fungal infections. J Am Board Fam Med, 25:734-744.

Calderone R.A and Cihlar R.L (eds). Fungal Pathogenesis: Principles and Clinical Applications. New York: Marcel Dekker; 2002.

Champoux J.J, Neidhardt F.C, Drew W.L and Plorde J.J (2004). Sherris Medical Microbiology: An Introduction to Infectious Diseases. 4th edition. McGraw Hill Companies Inc, USA.       

Gladwin M and Trattler B (2006). Clinical Microbiology Made Ridiculously Simple. 3rd edition. MedMaster, Inc., Miami, USA.

Larone D.H (2011). Medically Important Fungi: A Guide to Identification. Fifth edition. American Society of Microbiology Press, USA.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of Microorganisms, 12th edition. Pearson Benjamin Cummings Inc, USA.

Stephenson S.L (2010). The Kingdom Fungi: The Biology of Mushrooms, Molds and Lichens. First edition. Timber Press.

Sullivan D.J and Moran G.P (2014). Human Pathogenic Fungi: Molecular Biology and Pathogenic Mechanisms. Second edition. American Society of Microbiology Press, USA.

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