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Khamis, April 11, 2013

Designer Jeans: Made by Microbes?

Denim blue jeans have become popular ever since Levi Strauss and Jacob Davis first made them for California gold miners in 1873.
Now, companies that manufacture blue jeans are turning to microbiology to develop environmentally sound production methods that minimize toxic wastes. Moreover, microbiological method can provide abundant, renewable raw materials.

A softer denim, called "stone-washed," was introduced in the 1980. The fabric is not really washed with rocks. Enzymes, called cellulases, from Trichoderma fungus are use to digest some of the cellulose in the cotton, thereby softening it. Unlike many chemical reactions, enzymes usually operate at safe temperatures and pH. Moreover, enzymes are proteins, so they are readily degraded for removal from waste water.

Bacteria can produce both polyester with less environmental impact. Gluconacetobacter xylinus bacteria make cellulose by attaching glucose units to simple chains in the outer membrane of the bacterial cell wall. The cellulose microfibrils are extruded through pores in the outer membrane, and bundles of microfibrils then twist into ribbons.

Peroxide is a safer bleaching agent than chlorine and can be easily removed from fabric and waste water by enzymes.
Researchers at Novo Nordisk Biotech cloned a mushroom peroxidase gene in yeast and grew the yeasts in washing machine conditions. The yeast that survived the washing machine were selected as the peroxidase producers.

Chemical synthesis of indigo requires a high pH and produces waste that explodes in contact with air.
However, a California biotechnology biotechnology company, Genencor, has developed a method to produce indigo by using bacteria.
In the Genencor labs, researchers put the gene for conversion of the bacterial by-product indole to indigo from a soil bacterium, Pseudomonas putida, into Escherichia coli bacteria, which turned blue.

Microbes can even make plastic zippers and packaging material for jeans.
Over 25 bacteria make polyhydroxyalkanoate (PHA) inclusion granules as a food reserve. PHAs are similar to common plastics, and because they are made by bacteria, they are also readily degraded by many bacteria. PHAs could provide a biodegradable alternative to conventional plastic, which is made from petroleum.

source: Microbiology an Introduction, Tenth Edition

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