text: Synthetic biology could tackle the problems of nitrous oxide release during manufacturing, dependence on non-renewable petroleum.
  Author of the article:
  Joe Schwarz • Montreal Gazette Special
  Nylon thread is produced in a factory. “Toothbrush bristles, lingerie, swimwear, tents, toys, sutures, fishing nets, artificial turf, airbags, tire cord, auto parts and “invisible” thread for magic tricks are all nylon,” writes Joe Schwarcz. Shutterstock
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  A tower shaped like a giant test tube with flashing lights to simulate bubbling chemicals greeted visitors to DuPont’s “Wonder World of Chemistry” pavilion at the 1939 World’s Fair in New York. Inside, they were treated to a display of nylon, the company’s new miracle material “made from coal and air.” In 1935, DuPont chemist Wallace Carothers had combined adipic acid and hexamethylenediamine to make “6.6 nylon” with the terminology “6.6” derived from each component having six carbon atoms. Both are derived from cyclohexanol, which in turn was made from benzene obtained from the distillation of coal tar. The nitrogen needed to synthesize hexamethylenediamine came from air, so “made from coal and air”.
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  Viewers were amazed to see the nylon fiber produced before their eyes and then woven down below. Then comes an arm wrestling with the stockings to demonstrate the resistance of the material. A year after the fair, the nylon stockings went on sale to the public with five million sold on the first day! Nylon, touted as the first synthetic material said to be better than a natural material, became so popular that hawkers even tried to pawn silk stockings as nylon.
  At the time, no one worried about the environmental consequences of producing nylon or making it from non-renewable raw materials. Today, the nylon industry is huge, with Nylon 6 having also come into the picture. It was the brainchild of Paul Schleck at IG Farben in Germany who, in 1939, based on the work of Carothers, polymerized a small molecule containing six carbon atoms, caprolactam, into nylon 6. Some 18 million tons of combined nylons are now produced annually with a trade value of approximately $10 billion. Toothbrush bristles, lingerie, swimwear, tents, toys, sutures, fishing nets, artificial turf, airbags, tire cord, auto parts, and wire “invisible” for magic tricks are all made of nylon.
  The usefulness of nylon is indisputable, but there are questions about the environmental impact of plastic production on such a huge scale. There is the problem of raw materials coming from non-renewable oil. Then there is the issue of nitrous oxide release when cyclohexanol is treated with nitric acid to produce adipic acid. Nitrous oxide is commonly referred to as “laughing gas”, but its appearance in the atmosphere is no joke. It is a greenhouse gas, 300 times more powerful than carbon dioxide and represents about 10% of the greenhouse effect. Granted, nitrogen fertilizers and animal manure are far greater sources of nitrous oxide, but nylon production is a significant contributor, with around 30 grams produced for every pound of adipic acid.
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  The adipic acid industry now uses either catalysts or high temperatures to convert nitrous oxide waste into harmless nitrogen gas, but the ideal would be to produce adipic acid without any nitrous oxide formation. ‘nitrogen. Enter “synthetic biology”. Besides solving the problem of nitrous oxide, it can also solve the problem of using petroleum to make nylon.
  Synthetic biology is the manipulation of microbes such as yeasts, fungi, or bacteria to produce useful chemicals. In the simplest form, natural microbes are used along with the production of carbon dioxide by yeast to leaven dough, a classic example. By the 1970s, scientists had discovered methods to modify the DNA, that is, the genetic code of an organism, by inserting a gene from another organism. Bacillus thuringiensis (Bt) is a soil bacterium that produces a toxin that kills phytophagous insects. The gene that codes for this toxin has been isolated and inserted into the DNA of food crops such as corn and soy, allowing them to produce the toxin to deter insects, reducing the need for synthetic pesticides.
  This early form of recombinant DNA technology relied on the use of naturally occurring genes. The next objective was the possible synthesis of genes in the laboratory by linking together nucleotides, small molecules which are the building blocks of DNA. By the 1990s, the required methodologies had been developed and synthetic genes were inserted into the DNA of bacteria, essentially converting them into little factories to produce the chemicals encoded by the synthetic genes.
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  Going back to nylon, the researchers’ target was a gene that codes for an enzyme that converts glucose into adipic acid. The insertion of this gene into the DNA of a bacterium, E. coli for example, would then allow the genetically modified bacterium to transform glucose into adipic acid. Glucose is readily available from plants such as corn, which means adipic acid can be produced from a renewable resource, eliminating the need for petroleum. Also, there is no oxidation of cyclohexanol involved, so no production of nitrous oxide.
  An American company, Genomatica, has just developed a process using synthetic biology to produce not only adipic acid but also caprolactam. She has already made a ton of Nylon 6, showing that the technology works. It is now a question of increasing production, which is underway in partnership with the French Aquafil. This company’s factory in Slovenia is dedicated to the production of nylon from a renewable source with significantly reduced greenhouse gas emissions.
  Nylon production has come a long way since the shortages of World War II, when women were asked to give up their nylon stockings and turn them into parachutes. Now the challenge is to manufacture these stockings and parachutes in a “green” and environmentally friendly way.
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  Joe Schwarcz is director of the Office of Science and Society at McGill University (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3-4 p.m.
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