Biodeterioration is a terminology used to describe any undesirable change in the properties of a material caused by the vital activities of organisms.
Fungal growth requires suitable temperature, moisture and air (oxygen). Fungi are heterotrophs that acquire nutrients by absorption. They secrete hydrolytic enzymes (exoenzymes) and acids to decompose complex molecules into simpler ones that can be absorbed and used as nutrients. Hence, they are believed to be potential contributors to biodeterioration of different kinds of materials containing cellulose, silicate mineral (mica and orthoclase), iron and magnesium-bearing minerals (biotite, olivine, pyroxene) etc.
Fungi cause biodeterioration to many materials including:
- building materials
- animal feeds
- electrical equipment
- food including meat, fruits and grains
- fuel including jet fuel
- glass and optical equipments
- gunpowder
- leather
- monuments
- paint
- paper
- tobacco etc.
How are Fungi involved in biodeterioration?
The rate of biodeterioration depend on prevailing environmental conditions and the fungus involved. There are different mechanisms of biodegradation. These include microbial corrosion, hydrocarbon degradation and biodegradation of cellulose. Aspergillus niger, Chaetomium globosum, Scopulariopsis brevicaulis, Trichoderma koningii, Trichothecium roseum and Eurotium chevalieri are cellulolytic fungi. Their efficiency to degradate cellulosic (cellulose containing) materials is due to their ability to produce large amounts of cellulase enzymes.
Stachybotrys chartarum is a common fungus growing on paper (such as that covering gypsum wallboard) in damp buildings.
Some fungi cause blue stain and soft rot of wood, discolouration and loss of strength of cotton materials. Many fungi spoil food in storage. Aspergillus flavus grows on peanuts and many other substrates, producing a mycotoxin called aflatoxin, which contaminate food and causes liver damage. Fusarium graminearum grows on feed corn and produces the mycotoxin zearalenone that causes oestrogenic syndrome in animals.
Through the action of excreted oxalic and citric acids fungi can deteriorate marble, limestone, granite and basalt. Several species of fungi are involved in biodeterioration of stone monuments in different countries. Some of these fungi are Aspergillus elegans, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger, Aspergillus versicolor, Alternaria sp, Cladosporium cladosporioides, Cladosporium sphaerospermum, Cunninghamella echinulata, Curvularia lunata, Fusarium roseum, Gliocladium virens, Penicillium crustosum, Penicillium glabrum, Penicillium chrysogenum (=Penicillium notatum), Rhizopus arrhizus.
Biodeterioration is a problem worldwide. Several control measures have been applied to prevent the biodeterioration. These include use of fungicides, biological control, prevention of biodeterioration by control of environmental conditions, periodic cleaning of dirt, dust and spores, and use of radiation.