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Moulds are filamentous fungi. They are known as filamentous fungi because they have hyphae which are long branching filaments of fungi. Moulds are multicellular fungi that are non photosynthetic in nature. Unlike yeasts that are single celled or unicellular, moulds have multiple cells and thus are known as multicellular fungi. Moulds grow as filamentous branching strands of hyphae (which are long branching structures or filaments of some fungi such as moulds). They thrive most in moist or wet environment. Moulds grow by the expansion of their interconnected hyphae, and water is important in their growth. They 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. Moulds reproduce by both sexual and asexual reproduction methods; and their reproductive parts or structures are mainly spores.

Moulds produce their spores in large numbers; and these spores are readily spread or dispersed by air. Spores that fall or settle on favourable substrates can initiate a new phase of growth and develop into a new mycelium. A mycelium is a mass of branching intertwined or connected filaments. The whole mass of the hyphae formed by moulds is known as mycelium (pleural: mycelia). Some 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 and Rhizobium species are of immense industrial importance because of the metabolites that they produce. Moulds cause disease in humans and animals. Moulds are important spoilage organisms of food and raw materials for food production.


  • 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.
  • They play important roles in the production of various foods and beverages.
  • Moulds are important in the production of some antibiotics such as penicillin sourced from Penicillium chrysogenum and P. notatum.
  • Moulds are important in most fermentation process involved in wine production, food and other beverages.
  • 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 industrial microbiology for mass production of citric acid.
  • Aspergillus niger is also commonly used to produce citric acid, which is used to produce numerous products ranging from household cleaners, pharmaceuticals, foods, cosmetics, photography and construction.
  • Aspergillus species is also commonly used in large-scale fermentation in the production of alcoholic beverages.

Further reading

Bushell M.E (1998). Application   of   the   principles   of   industrial   microbiology   to   biotechnology (ed. Wiseman, A.) Chapman and Hall, New York.

Byong H. Lee (2015). Fundamentals of Food Biotechnology. Second edition. Wiley-Blackwell, New Jersey, United States.

Frazier W.C, Westhoff D.C and Vanitha N.M (2014). Food Microbiology. Fifth edition. McGraw-Hill Education (India) Private Limited, New Delhi, India.

Jay J.M (2005). Modern Food Microbiology. Fourth edition. Chapman and Hall Inc, New York, USA.

Bushell M.E (1998). Application   of   the   principles   of   industrial   microbiology   to   biotechnology (ed. Wiseman, A.) Chapman and Hall, New York.

Farida A.A (2012). Dairy Microbiology. First edition. Random Publications. New Delhi, India.

Nduka Okafor (2007). Modern industrial microbiology and biotechnology. First edition. Science Publishers, New Hampshire, USA.

Roberts D and Greenwood M (2003). Practical Food Microbiology. Third edition. Blackwell publishing Inc, USA.

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