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Heterotrophy - Definition

Heterotrophy - A definition

Heterotrophy (many + nourishment) is the process where existing organic molecules are used by an organism for its energy needs; in maintenance, growth and reproduction. All organic constituents in the organism are derived from pre-formed organic molecules, usually following their catabolism and anabolism.

Autotrophy is unknown among fungi, though many fungi associate closely with photobionts, either while the photobiont is living or following its death.

The consequence of heterotrophy is that a source of organic nutrition must be available for the continuation of the organism over time. Heterotrophy has led to a number of different functional approaches evolving within the fungi. LINK Further, heterotrophy has ensured that most organic carbon can be used as a food by one or other fungus.

Industrial Uses of Fungal Enzymes

Huge quantities of plant material are decomposed by microbes each year. The role of fungi is two fold; they enzymically degrade complex polymers, and absorb, transport, transform and store organic carbon and minerals resulting from the process. In this, fungi compete with bacteria, in particular. Decomposition of lignin is primarily a fungal process, and as cellulose is closely associated with the lignin in plant material, the importance of fungi is paramount in removal of plant litter. LINK

Cellulolignin is broken down by a complex of white-rot enzymes. The end product of digestion of cellulose is a monosaccharide such as glucose. The enzymes that degrade complex polymers have enormous commercial value. Enzymic digestion is used in the industrial production of single cell protein, organic acids, and biofuels such as ethanol.

Many fungi have been characterised for use in industry. The fungus Phanerochaete chrysosporium (Aphyllophorales) was characterised because of its production of lignin peroxidases. However, a large group of wood degrading fungi form a range of lignin and cellulose degrading enzymes, and in recent years a range of fungi have been characterised for more specific purposes. For instance, the cellulose degrading functions of Trichoderma, Fusarium and Penicillium have been examined with the goal of increasing enzymic activity, and therefore economic value in the paper-making industry.

The benefit of using fungi is obvious. Fungi produce and excrete a huge and complex array of enzymes. They can be maintained in factory conditions. They utilise a common waste as their source of energy. Filamentous fungi ramify through three-dimensional space.

A huge quantity of plant waste is produced from timber processing, cropping and food processing. If efficient ways to harness these processes could be found, then the waste could be used for the production of biodiesel, and reliance on fossil fuels for energy could be reduced.

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