Penicillium Characteristics & Uses

Penicillium is a fast-growing saprophytic fungus commonly known as blue or green mold. It belongs to the Ascomycota phylum of fungi kingdom. Penicillium, derived from the Latin word ‘Penicillus’ (meaning ‘Painter’s brush’), has a distinctive microscopic appearance due to which it is named so. It is ubiquitous in distribution and is found in soil, air, water, and living and dead organic matter. There are over 350 species of Penicillium that have medical and economic values. Penicillin, which is an antibiotic (introduced by Alexander Fleming in 1928) is obtained from Penicillium species: Penicillium chrysogenum (formerly known as Penicillium notatum). Penicillium is also used in the production of organic acids, enzymes, and cheese

Characteristics

Classification

Penicillium belongs to the phylum Ascomycota.

Habitat

Penicillium is ubiquitous in nature, which means it is found everywhere in air, water, and soil. Ideal environments for Penicillium include dust, decaying vegetation, stale food, compost, wood, certain food groups (fresh fruits, spices, vegetables, cereals), water-damaged buildings, etc. They have a saprophytic mode of nutrition and derive nutrients from dead and decaying matter, similar to other fungal genera including Rhizopus, Aspergillus, Mucor, etc. Penicillium needs moist and damp places to thrive, and they achieve maximum growth between 2o°C and 30°C.

Morphology

Macroscopic 

Penicillium spp. growing on a citrus fruit, blue and green mold

Penicillium appears as a white to bluish-green cotton-like structure that changes to olive-grey in some Penicillium species. It thrives on dead and decaying organic matter and can grow on fruits when left under favourable conditions.

Microscopic

Morphology of Penicillium species

Penicillium has a multicellular vegetative structure called mycelium, which is made up of multinucleated, septate, tubular-branched hyphae that spread all over the substratum to form a network. Some mycelia penetrate the substratum to absorb nutrients. Food is stored in the form of oil globules. At the end of the aerial hyphae, fruiting bodies called conidiophores are present along with specialised cells called phialide that further produce asexual spherical spores called conidiospores or conidia. This whole arrangement gives Penicillium a brush-like appearance.

Microscopic observation of Penicillium species, notice the brush-like appearance

Male and female gametangia (sex organs) are produced by mycelium cells, which further produce sexual spores called ascospores. Ascospores are arranged in asci in a bead-like structure. The cell wall of Penicillium is made up of chitin, glucose, and polysaccharide.

Reproduction

Asexual & Sexual Mode of Reproduction in Penicillium Species

Penicillium reproduces by vegetative, asexual, and sexual modes of reproduction.

Vegetative reproduction

Vegetative reproduction in Penicillium spp. takes place by fragmentation of hyphae. In some Penicillium species, reproduction takes place through sclerotia, which are compact mycelial structures formed under unfavourable conditions.

Asexual reproduction

Asexual reproduction in Penicillium spp. takes place through the sporulation of conidiophores and oidia (oidiospores).

Sexual reproduction

Sexual reproduction in Penicillium spp. takes place through the production of gametangia, Ascogonium (female gametangia), and Antheridia (male gametangia), which undergo karyogamy to form ascospores. The formation of ascospores is vital for sexual reproduction.

Uses

Many species of Penicillium are extremely important in the food, drug, and agriculture industries.

Ecological Uses

Penicillium spp. act as nature’s decomposers and help in maintaining ecological balance. They also play a key role in nutrient recycling, harbouring biodiversity, and pollutant degradation. They are valuable biological resources of secondary metabolites and enzymes. Due to their ability to break down xenobiotic compounds (pesticides, drugs, industrial chemical waste, environmental pollutants, etc), Penicillium spp. are used in bioremediation and helps to clean the environment.

Economic Importance

Many species of Penicillium are used in the industrial production of food, beverages, organic acids, enzymes, and antibiotics.

Food Production

Blue cheese made with Penicillium roqueforti

Some Penicillium species such as Penicillium camemberti and Penicillium roqueforti are used in the production of cheese. Penicillium nalgiovense is used in the casing of dry fermented sausages.

Brewing and wine industries

Different Penicillium species can alter the composition of the ingredients during fermentation. They are used to improve the taste, flavour, alcohol yield, and purity of beer and wine.

Organic Compound Production

Some Penicillium strains are used in the production of organic acids (fatty acid, citric acid, gluconic acid, tartaric acid), Enzymes (Amylases, proteases, cellulase, hemicellulose, lipase, and pectinase), cellulose, and hydrocarbons.

Some notable compounds produced by Penicillium spp. are as follows:

Alexander-Fleming (1881-1955) discovered Penicillin from Penicillium rubens on September 28, 1928

• Penicillin: It is an antibiotic obtained principally from P. chrysogenum and P. rubens. Sir Alexander Fleming discovered Penicillin in 1928.

• 3-oxoquinuclidine:  It is an important reagent base and catalyst, obtained from Penicillium jenseii.

• Limonene: It is a chemical compound found in citrus fruit peels and is used in food, pharmaceutical, and chemical manufacturing industries.

• 1,3,8-p-menthatriene: It is a plant metabolite and is used as a volatile oil component. It is obtained from Penicillium canescens.

• Formamidine: It is used in pest control and is obtained from Penicillium pusillum.

Biotechnological Importance

Penicillium species are capable of producing bioactive secondary metabolites such as antibacterials, antifungal, cholesterol-lowering drugs, tumour-suppressing compounds, and immunosuppressive drugs.

Key Notes

• Penicillium is a saprophytic fungus of the genus Ascomycetes that grow on dead and decaying matter for nutrition. Some of the species grow on fresh fruits and certain food products.

• Penicillium species are fast-growing fungi with white to bluish-green textures.

• It needs a suitable range of temperature between 20°C and 30°C to grow.

• Penicillium reproduces via vegetative, asexual, and sexual modes of reproduction.

• The name Penicillium originates from Latin for ‘Penicillus,’ meaning ‘painter’s brush’ because of the brush-like structure of the conidial spores.

• There are more than 350 species of Penicillium known to mankind.

• Penicillium species have significant ecologic and economic roles in bioremediation, food and brew industry, pharmaceuticals, and agriculture industries.

• Penicillium act as decomposers and helps in cleaning the environment. Some species can break down xenobiotic compounds like industrial chemical waste, drugs, pesticides, etc.

• Some Penicillium species are used in the production of important organic compounds such as enzymes, antibiotics, organic acids, cellulose, hydrocarbons, secondary metabolites, and immune-suppressive drugs, etc.

• There are some strains of Penicillium used in the production of different kinds of cheese.

• Penicillin, the most commonly known antibiotic is produced by Penicillium chrysogenum.  

• Some of the Penicillium species produce mycotoxins which cause diseases in plants and humans.