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Fungi prefer UV-treated diet.

Wood and crop wastes could yield industrial chemicals, a rich protein supplement for animals or an enzyme that breaks down cellulose. First, however, the plant wastes must be decomposed. A novel approach being studied at the State University of Campinas in Brazil involves irradiating the wastes with ultraviolet light (UV) and then feeding them to fungi newly isolated from the gut of a wood-eating insect.

Chemist Nelson Duran has found that the fungus Neurospore sitophila (TCB strain) thrives on lignin and cellulose--two important structural components of wood. It will also dine on rice straw. But when this fungal fare is pretreated with ultraviolet light irradiation for 1 to 12 hours, the fungi feast--and multiply--more rapidly.

For lignin, a 1-hour UV pretreatment with a mercury-vapor lamp (emitting a range of spectra at either 254 nanometers and higher or 300 nonmeters and higher) doubled the 10-day growth recorded for fungi dining on untreated material. Similar growth increases occurred with 6- or 12-hour pretreatments of cellulose, although for this material the lower spectral range appeared to make the diet more palatable. But irradiating rice straw for an hour brought the biggest gain--an eightfold increase in fungal growth over untreated straw.

Duran's analysis of lignin shows that the UV pretreatment initiates in the material's structure a chemical breakdown that is quite similar to the enzyme-activated degradation brought about by chemicals like ozone, chlorite or hydrogen peroxide. However, the fungi apparently see a difference in the UV-treated meal's digestability: Their growth on UV-treated rice straw was 20 to 40 percent higher than when their straw had been chemically treated.

Duran says the fungi could be harvested as a protein supplement for animal fodder. Alternatively, they could be used as little biological generators of cellulase, an enzyme that breaks down cellulose. It's even possible that the ultraviolet breakdown of lignin will yield an economical source of industrial chemicals such as acids and phenols, he says; that's what he's exploring now.
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Title Annotation:ultraviolet light
Author:Raloff, Janet
Publication:Science News
Date:Sep 21, 1985
Words:324
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