Applied Mycology

 

Role of Fungi in Biotechnology

Fungi are among the most important microorganisms used in biotechnology because of their rapid growth, ease of cultivation, ability to utilize inexpensive substrates, and capacity to produce a wide variety of commercially valuable metabolites and enzymes. They have extensive applications in the food, pharmaceutical, agricultural, and environmental sectors.

Major roles of fungi in biotechnology

• Food and fermentation industry: Fungi such as Saccharomyces cerevisiae are used in the production of bread, beer, wine, and other fermented foods. Species of Aspergillus and Penicillium are employed in the manufacture of soy sauce, cheese, and other fermented products.

• Production of industrial enzymes: Filamentous fungi secrete large quantities of extracellular enzymes such as amylases, cellulases, proteases, pectinases, and lipases. These enzymes are widely used in food processing, textile, paper, detergent, leather, and biofuel industries.

• Production of organic acids: Several fungi are commercially exploited for producing organic acids. For example, Aspergillus niger produces citric acid, while Aspergillus terreus produces itaconic acid, both of which have applications in the food, pharmaceutical, and chemical industries.

• Production of pharmaceuticals: Fungi synthesize numerous secondary metabolites of medicinal importance, including antibiotics (penicillin from Penicillium chrysogenum), immunosuppressants (cyclosporin A from Tolypocladium inflatum), cholesterol-lowering drugs (lovastatin from Aspergillus terreus), and antifungal agents.

• Agricultural applications: Mycorrhizal fungi improve nutrient uptake and plant growth, while species of Trichoderma, Beauveria, and Metarhizium are used as eco-friendly biological control agents against plant pathogens, insect pests, and nematodes.

• Environmental biotechnology: Fungi degrade complex organic pollutants such as lignin, dyes, pesticides, petroleum hydrocarbons, and plastics through extracellular enzymes, making them valuable agents for bioremediation and waste management.

Why fungi are preferred in biotechnology

• Rapid growth and easy large-scale cultivation.
• High secretion of extracellular enzymes simplifies downstream processing.
• Ability to grow on inexpensive agricultural and industrial wastes.
• Production of a diverse range of primary and secondary metabolites.
• Amenable to genetic improvement and metabolic engineering.

Applications of Fungi in the Food Industry

Fungi have been used in food production for thousands of years and are indispensable to modern food biotechnology. Their ability to ferment carbohydrates, produce enzymes, synthesize organic acids, and modify food flavour and texture has led to their widespread use in the manufacture of beverages, bakery products, dairy products, fermented foods, and protein-rich foods. Many fungi also serve as sources of food additives and processing aids.

1. Fermentation

Fermentation is a metabolic process in which fungi convert carbohydrates into alcohol, carbon dioxide, organic acids, or other metabolites under controlled conditions. It enhances the nutritional value, flavour, texture, digestibility, and shelf life of food.

In brewing or wine making industry alcohol is the important product. The other by-product which is carbon dioxide was formerly allowed to escape as a useless thing. Now carbon dioxide is also considered a valuable by-product. It is collected, solidified and sold as “dry ice”. In the baking or bread- making industry CO2 is the useful product. 

The yeasts secrete the enzyme complex called zymase which brings about conversion of sugar into alcohol. The yeasts lack diastase. So, they cannot break starch into sugar. 

A group of fungi, popularly known as the moulds, secrete a whole range of enzymes for fermentation of complex carbohydrates. 

In producing industrial alcohol, moulds are employed as starters to bring about scarification of the starch. At the second stage yeast is employed to act on the sugar.

The moulds commonly used for purpose of scarification are Mucor racemosus. M. rouxii and some species of Rhizopus. 

Other important fungal species include:

• Saccharomyces cerevisiae (baker's and brewer's yeast)
• Aspergillus oryzae
• Rhizopus oligosporus
• Monascus purpureus

Examples: 

Food product	Fungus used	Role
Beer	Saccharomyces cerevisiae	Alcohol fermentation
Wine	Saccharomyces cerevisiae	Ethanol production
Sake	Aspergillus oryzae; Saccharomyces cerevisiae	Starch saccharification and alcohol production
Soy sauce	Aspergillus oryzae	Enzyme production and flavour development
Miso	Aspergillus oryzae	Fermentation of soybean paste
Tempeh	Rhizopus oligosporus	Fermentation of soybeans
Red fermented rice	Monascus purpureus	Pigment and flavour production

2. Baking Industry

The baking industry primarily utilizes the yeast Saccharomyces cerevisiae, commonly known as baker's yeast.

Yeast ferments sugars present in the dough to produce:

• Carbon dioxide (CO₂)
• Ethanol

The carbon dioxide becomes trapped within the gluten network of the dough, causing it to rise. During baking, ethanol evaporates while the dough sets into a soft and porous structure.

Glucose → 2 Ethanol + 2 CO₂ + Energy

Applications

• Bread
• Pizza
• Cakes
• Buns
• Doughnuts

3. Flavour and Texture Development

Several fungi improve the flavour, aroma, colour, and texture of food through enzymatic degradation of proteins, fats, and carbohydrates.

(A) Cheese Ripening

Species of Penicillium are responsible for the characteristic flavour and texture of several cheeses.

These fungi secrete:

• Proteases that hydrolyse milk proteins.
• Lipases that break down milk fats.

These reactions generate amino acids, fatty acids, aldehydes, ketones, and esters that impart characteristic flavours and aromas.

Cheese	Fungus	Function
Roquefort	Penicillium roqueforti	Blue veins, strong flavour
Camembert	Penicillium camemberti	Soft texture and creamy flavour
Brie	Penicillium camemberti	Surface ripening

(B) Fermented Soy Products

Aspergillus oryzae produces:

• Amylases
• Proteases
• Lipases

These enzymes hydrolyse starch, proteins, and lipids, resulting in enhanced umami flavour and improved digestibility.

(C) Mushroom-Based Foods

Edible mushrooms include:

• Agaricus bisporus
• Pleurotus ostreatus
• Lentinula edodes

They are valued for their:

• Pleasant flavour
• Umami taste
• Meaty texture
• High nutritional value

4. Production of Organic Acids

Many fungi produce commercially important organic acids through aerobic fermentation.

Key Points

• Citric acid is the most commercially important fungal organic acid, accounting for the largest share of industrial organic acid production worldwide.
• Aspergillus niger is the workhorse fungus for the commercial production of citric acid and gluconic acid due to its high yield, rapid growth, and Generally Recognized as Safe (GRAS) status for many industrial applications.
• Most fungal organic acids are produced by submerged aerobic fermentation using inexpensive carbohydrate-rich substrates such as molasses or starch hydrolysates.
• Besides their role as food acidulants and preservatives, fungal organic acids are extensively used in the pharmaceutical, cosmetic, detergent, polymer, and chemical industries.

Organic acid	Major fungal producer	Substrate/ Raw material	Industrial production conditions	Major applications
Citric acid	Aspergillus niger	Molasses, sucrose, glucose	Aerobic fermentation; high sugar concentration; low pH (≈2); limited manganese ions	Acidulant and preservative in foods and beverages, pharmaceuticals, cosmetics, detergents
Gluconic acid	Aspergillus niger (A. foetidus also used)	Glucose	Aerobic fermentation with glucose oxidase activity	Food additive, pharmaceutical formulations, mineral supplements (calcium gluconate), cleaning agents
Itaconic acid	Aspergillus terreus	Glucose, molasses, starch hydrolysates	Aerobic submerged fermentation	Production of synthetic resins, biodegradable plastics, acrylic fibres, adhesives, and coatings
Fumaric acid	Rhizopus arrhizus (R. oryzae)	Glucose and other carbohydrates	Aerobic fermentation	Food acidulant, bakery products, beverages, confectionery, pharmaceutical formulations
Lactic acid	Rhizopus oryzae	Glucose, starch hydrolysates	Aerobic fermentation	Food preservative, biodegradable polylactic acid (PLA), cosmetics, pharmaceuticals
Malic acid	Aspergillus flavus, A. oryzae, Rhizopus spp.	Sugars	Fermentation under controlled pH and aeration	Food acidulant, beverages, confectionery, pharmaceuticals
Oxalic acid	Aspergillus niger	Sugars	Aerobic fermentation	Textile processing, metal cleaning, leather industry, chemical synthesis (limited food use due to toxicity)

5. Production of Industrial Enzymes

Fungi are preferred industrial producers because they naturally secrete extracellular enzymes, making enzyme recovery easier and more economical.

Enzyme	Major fungal source	Applications
Amylase	Aspergillus oryzae, A. niger	Hydrolyses starch into simple sugars. Used in bread making to improve dough quality and loaf volume, in brewing for starch conversion, in the production of glucose and maltose syrups, and in the manufacture of confectionery products.
Protease	Aspergillus oryzae, A. niger	Hydrolyses proteins into peptides and amino acids. Used in cheese manufacture, meat tenderization, baking to improve dough handling, production of protein hydrolysates, soy sauce fermentation, and clarification of beverages.
Lipase	Rhizopus spp., Aspergillus spp.	Hydrolyses fats and oils. Used for cheese ripening and flavour development, production of dairy products, synthesis of flavour esters, modification of edible oils, and processing of cocoa and chocolate products.
Cellulase	Trichoderma reesei, Aspergillus niger	Degrades cellulose into glucose. Used in fruit and vegetable processing, extraction of fruit juices, improvement of animal feed digestibility, coffee bean processing, and production of bioethanol from agricultural residues.
Pectinase	Aspergillus niger	Breaks down pectin in plant cell walls. Widely used for clarification and increased yield of fruit juices and wines, extraction of fruit pulps, improvement of fruit mash processing, and reduction of juice viscosity.
Xylanase	Trichoderma reesei, Aspergillus spp.	Degrades hemicellulose (xylan). Used in baking to improve dough elasticity and bread volume, enhance texture of baked products, improve cereal processing, and increase extraction efficiency of plant materials.
Invertase (β-fructofuranosidase)	Saccharomyces cerevisiae	Hydrolyses sucrose into glucose and fructose (invert sugar). Used in chocolate and confectionery industries to produce soft-centred candies, manufacture of invert sugar syrup, artificial honey production, and beverage processing.
Lactase (β-galactosidase)	Kluyveromyces lactis, Aspergillus oryzae	Hydrolyses lactose into glucose and galactose. Used in the production of lactose-free milk and dairy products, improvement of sweetness in dairy foods, prevention of lactose crystallization in ice cream and condensed milk, and manufacture of dairy ingredients for lactose-intolerant consumers.

Fungal enzymes are preferred in industrial food processing because they:

• Are secreted extracellularly, making their recovery and purification easier.
• Can be produced economically on inexpensive substrates through fermentation.
• Exhibit high catalytic efficiency under industrial conditions.
• Improve food quality, flavour, texture, digestibility, and shelf life.
• Reduce processing time, energy consumption, and production costs.
• Are generally recognized as safe (GRAS) when produced by approved fungal species such as Aspergillus oryzae and Saccharomyces cerevisiae.

Mycoproteins

Mycoprotein is a protein-rich food produced from the biomass of filamentous fungi grown by controlled fermentation. It is a sustainable, nutritious alternative to animal protein and is widely used in the preparation of meat substitutes.

Production

The most widely used fungus for commercial mycoprotein production is Fusarium venenatum.

1. Fusarium venenatum is grown under aerobic submerged fermentation in large fermenters.
2. The culture medium contains glucose or starch-derived carbohydrates, ammonia (as a nitrogen source), minerals, vitamins, and oxygen.
3. During fermentation, the fungus forms a network of protein-rich mycelial biomass.
4. The biomass is harvested and heat-treated to reduce its RNA content, preventing excessive uric acid accumulation upon consumption.
5. The treated biomass is mixed with suitable binders (e.g., egg albumin or plant-based binders) and processed into various food products.

Nutritional Value

Mycoprotein is considered a high-quality food because it contains:

• High protein content (approximately 40–50% dry weight)
• All essential amino acids
• High dietary fibre (mainly β-glucans and chitin)
• Low fat and low saturated fat
• Cholesterol-free
• Rich in vitamins (especially B-complex) and minerals

Applications

Mycoprotein is widely used in the manufacture of:

• Vegetarian and vegan meat substitutes
• Burgers
• Sausages
• Nuggets
• Minced meat alternatives
• Ready-to-eat meals
• High-protein functional foods

The best-known commercial product is Quorn™, marketed in many countries as a meat alternative.

Advantages

• Sustainable source of high-quality protein
• Requires less land and water than livestock farming
• Lower greenhouse gas emissions compared to meat production
• Rapid production through microbial fermentation
• High fibre content promotes satiety and digestive health
• Suitable for vegetarian and flexitarian diets

Limitations

• Some individuals may develop allergic reactions to fungal proteins.
• The biomass must be heat-treated to reduce RNA content before consumption.
• Production requires specialized fermentation facilities.

Feature	Description
Producer organism	Fusarium venenatum
Commercial product	Quorn™
Production method	Aerobic submerged fermentation
Protein content	40–50% (dry weight)
Major applications	Meat substitutes, burgers, sausages, nuggets, ready-to-eat foods
Major advantages	Sustainable, high protein, low fat, cholesterol-free

Secondary Metabolites of Fungi in Pharmaceutical Preparations

Secondary metabolites are low-molecular-weight organic compounds produced by fungi during the stationary phase of growth. Unlike primary metabolites, they are not directly involved in normal growth, development, or reproduction, but provide ecological advantages such as defense against competitors and environmental stress. Many fungal secondary metabolites possess potent biological activities and are widely used as pharmaceuticals.

Fungi produce a diverse range of bioactive compounds with antibacterial, antifungal, immunosuppressive, hypocholesterolemic, antitumor, and vasoactive properties. These compounds have revolutionized modern medicine and are extensively used in clinical practice.

1. Antibiotics

Antibiotics are secondary metabolites produced by microorganisms that, in low concentrations, inhibit the growth of or destroy other microorganisms without causing significant harm to the host when used therapeutically. Antibiotics are the most significant fungal secondary metabolites used to inhibit or kill pathogenic microorganisms.

Key Characteristics of Antibiotics

• Produced naturally by fungi or bacteria.
• Secondary metabolites synthesized mainly during the stationary phase.
• Active at very low concentrations.
• Possess selective toxicity against microorganisms.
• Widely used in medicine to treat infectious diseases.

Secondary metabolite	Producer fungus	Pharmaceutical application
Penicillin	Penicillium chrysogenum (formerly P. notatum)	Broad-spectrum antibiotic used to treat bacterial infections such as pneumonia, streptococcal infections, and syphilis.
Cephalosporins	Acremonium chrysogenum (formerly Cephalosporium acremonium)	β-lactam antibiotics effective against a wide range of Gram-positive and Gram-negative bacteria.
Griseofulvin	Penicillium griseofulvum	Antifungal drug used in the treatment of dermatophytic infections (ringworm, athlete's foot, tinea).

2. Immunosuppressants

The immune system recognizes transplanted organs (e.g., kidney, liver, heart) as foreign and attempts to destroy them, a process known as graft rejection. Immunosuppressant drugs inhibit specific immune responses, allowing the transplanted organ to function normally.

They are also used in autoimmune diseases, where the immune system mistakenly attacks the body's own tissues, such as in rheumatoid arthritis, psoriasis, and lupus.

Compound	Producer fungus	Application
Cyclosporin A	Tolypocladium inflatum	Prevents organ transplant rejection and treats autoimmune diseases
Mycophenolic acid	Penicillium brevicompactum	Used (as mycophenolate derivatives) in organ transplantation and autoimmune disorders by inhibiting lymphocyte proliferation

3. Cholesterol-Lowering Drugs (Statins)

Statins are not required for the normal growth or reproduction of the fungus. They are synthesized during the stationary phase of growth as secondary metabolites, likely providing ecological advantages by inhibiting the growth of competing microorganisms.

Statins act by competitively inhibiting HMG-CoA reductase (3-hydroxy-3-methylglutaryl coenzyme A reductase), the rate-limiting enzyme in the mevalonate pathway responsible for cholesterol biosynthesis in the liver.

Statins are widely prescribed for:

• Hypercholesterolemia (high blood cholesterol)
• Prevention of coronary artery disease
• Reduction of heart attack and stroke risk
• Management of atherosclerosis

Statin	Producer fungus	Remarks
Lovastatin (Monacolin K)	Aspergillus terreus	First naturally occurring statin used clinically
Compactin (Mevastatin)	Penicillium citrinum	First statin discovered; served as the prototype for later statins
Monacolin K	Monascus ruber/Monascus purpureus	Chemically identical to lovastatin; found in red yeast rice

4. Ergot Alkaloids

Ergot alkaloids are a class of nitrogen-containing (indole) alkaloids produced mainly by the fungus Claviceps purpurea, an obligate parasite of cereal crops such as rye, wheat, barley, and other grasses. They are synthesized in the fungal sclerotia (ergots) that replace the developing grains.

Although ergot alkaloids are mycotoxins at high doses, they have significant therapeutic value when administered in controlled amounts.

Secondary metabolite	Producer fungus	Application
Ergotamine	Claviceps purpurea	Treatment of migraine headaches and vascular disorders.
Ergometrine (Ergonovine)	Claviceps purpurea	Stimulates uterine contractions and is used to control postpartum haemorrhage.

Pharmaceutical significance

• Used in obstetrics to control excessive bleeding after delivery.
• Used in the treatment of migraine due to their vasoconstrictive action.
• Serve as starting materials for semisynthetic drugs, such as bromocriptine and cabergoline, which are used to treat:
  • Parkinson's disease
  • Hyperprolactinaemia
  • Acromegaly
• Have contributed significantly to the development of neuropharmacological drugs.

Toxicity

Consumption of grains contaminated with Claviceps purpurea sclerotia can cause ergotism, historically known as "St. Anthony's Fire."

Symptoms include:

• Severe vasoconstriction leading to reduced blood supply
• Burning pain in the limbs
• Gangrene
• Muscle spasms and convulsions
• Hallucinations and neurological disturbances
• In severe cases, death

5. Anticancer and Other Bioactive Metabolites

Bioactive metabolites are fungal secondary metabolites that exert a biological effect on living organisms. Their activities include:

• Anticancer
• Antiviral
• Antibacterial
• Antifungal
• Antioxidant
• Anti-inflammatory
• Immunomodulatory
• Antiparasitic

Many of these compounds serve as lead molecules for drug discovery rather than being widely marketed drugs.

Examples include:

Compound	Producer fungus	Biological activity	Status/Application
Cordycepin	Cordyceps militaris	Anticancer, antiviral, anti-inflammatory, immunomodulatory	Investigational anticancer agent and nutraceutical
Fumagillin	Aspergillus fumigatus	Anti-angiogenic, antiparasitic	Used against microsporidiosis; studied in cancer therapy
Mycophenolic acid	Penicillium brevicompactum	Immunosuppressive	Clinically used as mycophenolate mofetil in organ transplantation
Gliotoxin	Aspergillus fumigatus	Immunosuppressive, antimicrobial	Mainly a research compound due to toxicity
Cytochalasins	Chaetomium, Aspergillus spp.	Inhibit actin polymerization	Widely used in cell biology research; potential anticancer leads

Why are they called "anticancer metabolites"?

Certain fungal metabolites can inhibit cancer by:

• Blocking cell division
• Inducing apoptosis (programmed cell death)
• Preventing angiogenesis (formation of new blood vessels that supply tumors)
• Modulating immune responses
• Inhibiting DNA or RNA synthesis

For example:

• Cordycepin interferes with RNA synthesis and can trigger apoptosis in several cancer cell lines.
• Fumagillin inhibits methionine aminopeptidase-2 (MetAP2), suppressing angiogenesis and limiting tumor growth.

Fungi as Biofertilizers

Fungal biofertilizers are formulations containing beneficial fungi that enhance plant growth by improving the availability and uptake of nutrients, particularly phosphorus, and by promoting root development. Unlike chemical fertilizers, fungal biofertilizers do not directly supply nutrients but increase their accessibility to plants through natural biological processes.

 

Types of Fungal Biofertilizers

1. Mycorrhizal Fungi

Mycorrhiza is a mutualistic association between fungal hyphae and plant roots, in which both partners benefit. The fungus receives carbohydrates from the plant, while the plant gains improved access to water and mineral nutrients.

The most widespread type is the Arbuscular Mycorrhiza (AM) formed by fungi such as Glomus, Gigaspora, Acaulospora, and Rhizophagus.

Mechanism of action

• Hyphae extend beyond the root zone, increasing the surface area for absorption.
• Facilitate the uptake of relatively immobile nutrients, especially phosphorus (P), as well as zinc (Zn) and copper (Cu).
• Improve water absorption and soil aggregation.
• Enhance tolerance to drought, salinity, and certain soil-borne pathogens.

2. Phosphate-Solubilizing Fungi (PSF)

Many soil phosphates occur in insoluble forms that cannot be utilized by plants. Phosphate-solubilizing fungi convert these into soluble forms by secreting organic acids (such as citric, oxalic, and gluconic acids) and phosphatase enzymes.

Common phosphate-solubilizing fungi include:

Aspergillus niger

Penicillium bilaii

Penicillium simplicissimum

Mechanism of action 

• Secretion of organic acids lowers soil pH.
• Organic acids chelate calcium, iron, and aluminium ions bound to phosphate.
• Insoluble phosphates are converted into soluble phosphate ions that can be absorbed by plant roots.

Advantages of Fungal Biofertilizers

• Increase phosphorus and micronutrient uptake.
• Promote root growth and overall plant development.
• Improve drought tolerance and resistance to environmental stresses.
• Enhance soil fertility and soil structure.
• Reduce dependence on chemical fertilizers.
• Support sustainable and eco-friendly agriculture.

Examples of fungi as biofertilizer:

Biofertilizer fungus	Major function
Glomus spp.	Forms arbuscular mycorrhiza and enhances phosphorus uptake
Gigaspora spp.	Improves nutrient and water absorption
Rhizophagus irregularis	Enhances plant growth and stress tolerance
Aspergillus niger	Solubilizes insoluble phosphate in soil
Penicillium bilaii	Increases phosphorus availability and crop yield

Mycotoxins

Mycotoxins are toxic, low-molecular-weight secondary metabolites produced by certain filamentous fungi that contaminate agricultural commodities, food, and animal feed. They are synthesized mainly during the stationary phase of fungal growth under favourable environmental conditions such as high humidity and temperature. Mycotoxins are generally heat stable, and therefore may persist even after food processing, posing serious risks to human and animal health.

Key Points

• Mycotoxins are secondary metabolites, not essential for fungal growth but highly toxic to humans and animals.
• Aflatoxin B₁ is the most potent naturally occurring hepatocarcinogen and is classified as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC).
• Prevention relies primarily on good agricultural practices, proper storage, and regular monitoring, as many mycotoxins are heat stable and cannot be completely destroyed by normal cooking.

Major Mycotoxins and Their Effects

Mycotoxin	Producer fungus	Common contaminated commodities	Major toxic effects
Aflatoxins (B₁, B₂, G₁, G₂)	Aspergillus flavus, A. parasiticus	Groundnuts, maize, rice, spices, tree nuts	Hepatotoxic, hepatocarcinogenic, immunosuppressive
Ochratoxin A	Aspergillus ochraceus, Penicillium verrucosum	Cereals, coffee, dried fruits, wine	Nephrotoxic, immunotoxic, possible carcinogen
Patulin	Penicillium expansum	Apples, apple juice and other fruits	Gastrointestinal disorders, neurotoxic effects
Fumonisins	Fusarium verticillioides, F. proliferatum	Maize and maize products	Neurotoxicity, liver and kidney damage, oesophageal cancer
Zearalenone	Fusarium graminearum	Maize, wheat, barley	Estrogenic effects, infertility and reproductive disorders
Trichothecenes (e.g., DON, T-2 toxin)	Fusarium spp.	Wheat, barley, oats, maize	Inhibition of protein synthesis, vomiting, immune suppression
Ergot alkaloids	Claviceps purpurea	Rye and other cereals	Ergotism, vasoconstriction, gangrene, convulsions

Conditions Favouring Mycotoxin Production

Mycotoxin production depends on environmental conditions and fungal growth. Major factors include:

• High moisture content and humidity
• Warm temperatures (20–35°C)
• Poor storage conditions
• Mechanical damage to grains and fruits
• Insect infestation
• Prolonged storage of food and feed

Economic Importance

Mycotoxins cause significant economic losses worldwide by:

• Reducing crop quality and market value.
• Causing rejection of contaminated food exports.
• Lowering livestock productivity.
• Increasing healthcare and food safety costs.

Prevention and Control

Effective management of mycotoxins involves preventing fungal growth and minimizing toxin formation.

Pre-harvest measures

• Cultivation of resistant crop varieties
• Proper irrigation and field sanitation
• Control of insect pests and plant diseases
• Timely harvesting

Post-harvest measures

• Rapid drying of grains to safe moisture levels
• Storage under cool and dry conditions
• Prevention of insect infestation
• Regular monitoring of food and feed

Biological and Chemical Control

• Use of non-toxigenic strains of Aspergillus flavus to competitively exclude toxin-producing strains.
• Application of biological detoxifying microorganisms and enzymes.
• Addition of mycotoxin-binding agents (adsorbents) in animal feed to reduce toxin absorption.

Fungi as Biological Control Agents

Biological control is the use of living organisms or their products to suppress the population of plant pathogens, weeds, insect pests, and plant-parasitic nematodes. Fungi used for this purpose are known as mycobiocontrol agents or fungal biocontrol agents. They provide an eco-friendly alternative to chemical pesticides and play an important role in sustainable agriculture and integrated pest management (IPM).

Mechanisms of Fungal Biocontrol

Fungal biocontrol agents suppress pests and pathogens through one or more of the following mechanisms:

• Mycoparasitism: Direct parasitism of pathogenic fungi by biocontrol fungi.
• Competition: Competition with pathogens for nutrients and space.
• Antibiosis: Production of antibiotics and toxic metabolites that inhibit pathogens.
• Enzymatic degradation: Secretion of cell wall-degrading enzymes such as chitinases, glucanases, proteases, and cellulases.
• Induced systemic resistance (ISR): Activation of the plant's defense mechanisms against future pathogen attacks.

1. Mycofungicides

Mycofungicides are beneficial fungi used to suppress or eliminate plant pathogenic fungi that cause diseases such as damping-off, root rot, wilt, blight, and collar rot. They colonize the rhizosphere or plant surface and inhibit pathogens through mycoparasitism, competition for nutrients and space, production of antibiotics (antibiosis), secretion of cell wall-degrading enzymes (e.g., chitinases and glucanases), and induction of systemic resistance in plants. They are commonly applied as seed treatments, soil amendments, or foliar formulations and are important components of Integrated Pest Management (IPM).

Biocontrol fungus	Target pathogen	Mode of action
Trichoderma harzianum	Rhizoctonia solani, Sclerotium rolfsii, Fusarium spp.	Mycoparasitism, antibiosis, enzyme production
Trichoderma viride	Fusarium, Pythium, Rhizoctonia	Competition and production of lytic enzymes
Coniothyrium minitans	Sclerotinia sclerotiorum	Parasitizes sclerotia and inhibits survival of the pathogen

Applications

• Control of damping-off, root rot, wilt, and collar rot diseases.
• Seed treatment and soil application.
• Reduction in the use of chemical fungicides.

2. Mycoherbicides

Mycoherbicides are fungi employed for the biological control of weeds. These fungi infect specific weed species, reducing their growth, reproduction, and competitiveness without causing significant damage to crop plants. Their high host specificity makes them environmentally safe alternatives to chemical herbicides. Mycoherbicides are particularly useful in controlling invasive weeds in agricultural fields, forests, and aquatic ecosystems while minimizing environmental pollution.

Fungus	Target weed	Application
Colletotrichum gloeosporioides f. sp. aeschynomene	Northern jointvetch (Aeschynomene virginica)	Commercial mycoherbicide for rice and soybean fields
Phytophthora palmivora	Milkweed vine (Morrenia odorata)	Biological control of invasive vines
Puccinia chondrillina	Skeleton weed (Chondrilla juncea)	Classical biological control in cereal-growing regions

Advantages

• High host specificity.
• Minimal impact on non-target plants.
• Environmentally safe alternative to herbicides.

3. Mycoinsecticides

Mycoinsecticides are entomopathogenic fungi that infect and kill insect pests. Unlike chemical insecticides, these fungi penetrate the insect cuticle directly and proliferate within the insect body, eventually causing death through tissue destruction and toxin production. After the insect dies, fungal spores develop on the cadaver and spread to infect other susceptible insects. Mycoinsecticides are widely used against aphids, whiteflies, termites, beetles, caterpillars, and locusts in agriculture and horticulture.

Fungus	Target insects
Beauveria bassiana	Whiteflies, aphids, beetles, termites, caterpillars
Metarhizium anisopliae	Grasshoppers, termites, beetles, locusts
Lecanicillium lecanii (formerly Verticillium lecanii)	Aphids, whiteflies, scale insects
Isaria fumosorosea	Whiteflies, thrips, psyllids

Applications

• Integrated pest management (IPM).
• Biological control in organic farming.
• Reduction in synthetic insecticide use.

4. Myconematicides (Nematophagous Fungi)

Myconematicides are fungi that suppress plant-parasitic nematodes, such as root-knot and cyst nematodes, which cause severe yield losses in crops. These fungi employ diverse mechanisms, including trapping nematodes with specialized adhesive networks or constricting rings, parasitizing nematode eggs and females, and producing extracellular enzymes that degrade nematode tissues. Their use reduces nematode populations, improves root health, and decreases dependence on chemical nematicides, making them valuable tools for sustainable crop production.

Fungus	Target	Mode of action
Purpureocillium lilacinum (formerly Paecilomyces lilacinus)	Root-knot and cyst nematodes	Egg parasitism
Pochonia chlamydosporia	Nematode eggs	Egg parasitism and enzymatic degradation
Arthrobotrys oligospora	Free-living and plant-parasitic nematodes	Adhesive hyphal traps
Dactylella spp.	Soil nematodes	Constricting rings and trapping structures

Applications

• Management of root-knot nematodes (Meloidogyne spp.).
• Reduction of nematode populations in horticultural and agricultural crops.
• Improvement of root health and crop yield.

Advantages of Fungal Biocontrol Agents

• Eco-friendly and biodegradable.
• Highly specific to target organisms.
• Safe for humans, animals, and beneficial insects.
• Reduce dependence on chemical pesticides.
• Compatible with Integrated Pest Management (IPM).
• Lower risk of environmental pollution and pesticide residues.
• Some fungi also promote plant growth and induce systemic resistance.

Limitations

• Effectiveness depends on environmental conditions such as humidity and temperature.
• Slower action compared to chemical pesticides.
• Limited shelf life of some formulations.
• Some agents have a narrow host range.

Medical Mycology

Medical mycology is the branch of microbiology that deals with the study of fungi causing diseases (mycoses) in humans and animals, including their identification, pathogenesis, diagnosis, treatment, and prevention. Of the thousands of known fungal species, only about 300 species are known to cause human diseases. Fungal infections range from superficial skin infections to life-threatening systemic diseases, particularly in immunocompromised individuals.

Characteristics of Pathogenic Fungi

Pathogenic fungi possess several characteristics that enable them to infect the host:

• Most are eukaryotic organisms with chitinous cell walls.
• They reproduce by spores that facilitate dissemination.
• Many are opportunistic pathogens, causing disease when host immunity is weakened.
• Some fungi exhibit thermal dimorphism, existing as moulds in the environment (25°C) and as yeasts in host tissues (37°C).
• Infection occurs through inhalation of spores, direct contact, traumatic implantation, or overgrowth of normal flora.

Classification of Mycoses

Fungal diseases are classified according to the site of infection.

Type of mycosis	Site of infection	Characteristic features	Major causative fungi	Examples of diseases
Superficial mycoses	Outermost layer of skin and hair shaft	Limited to the stratum corneum and hair; do not invade living tissues; mainly cosmetic	Hortaea werneckii, Piedraia hortae, Trichosporon spp.	Tinea nigra, Black piedra, White piedra
Cutaneous mycoses (Dermatophytoses)	Keratinized tissues (skin, hair and nails)	Dermatophytes invade keratinized tissues causing itching, scaling and inflammation	Trichophyton, Microsporum, Epidermophyton	Ringworm (Tinea corporis), Athlete's foot (Tinea pedis), Tinea capitis, Onychomycosis (Tinea unguium)
Subcutaneous mycoses	Dermis, subcutaneous tissues and lymphatics	Acquired through traumatic implantation of fungal spores from soil or plant material; chronic localized infections	Sporothrix schenckii, Fonsecaea spp., Cladophialophora carrionii, Madurella mycetomatis	Sporotrichosis, Chromoblastomycosis, Eumycetoma
Systemic (Deep) mycoses	Internal organs, especially lungs; may disseminate to multiple organs	Usually acquired by inhalation of spores; many causative fungi are thermally dimorphic	Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides brasiliensis	Histoplasmosis, Blastomycosis, Coccidioidomycosis, Paracoccidioidomycosis
Opportunistic mycoses	Various organs depending on the host's immune status	Occur mainly in immunocompromised individuals such as AIDS patients, transplant recipients and cancer patients	Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans, Rhizopus spp., Mucor spp., Pneumocystis jirovecii	Candidiasis, Aspergillosis, Cryptococcosis, Mucormycosis, Pneumocystis pneumonia (PCP)

Diagnosis of Fungal Infections

Diagnosis involves clinical examination supported by laboratory investigations.

• Direct microscopic examination using KOH mount to detect fungal elements.
• Culture on Sabouraud Dextrose Agar (SDA) for fungal isolation and identification.
• Histopathological examination using special stains such as Periodic Acid-Schiff (PAS) and Gomori Methenamine Silver (GMS).
• Serological and antigen detection tests for specific fungal infections.
• Molecular techniques such as PCR for rapid and accurate identification.

Treatment

The choice of antifungal drug depends on the type and severity of infection.

Drug	Major use
Amphotericin B	Severe systemic mycoses
Fluconazole	Candidiasis and cryptococcosis
Itraconazole	Histoplasmosis, sporotrichosis, dermatophytosis
Voriconazole	Invasive aspergillosis
Terbinafine	Dermatophytosis and onychomycosis

Prevention

• Maintain good personal hygiene.
• Keep skin clean and dry.
• Avoid sharing personal items such as towels and footwear.
• Wear protective footwear in public areas.
• Promptly treat superficial fungal infections.
• Use sterile instruments in healthcare settings.
• Protect immunocompromised individuals from exposure to fungal spores.