In the 1930s, the DuPont company created the world’s first nylon, a synthetic polymer made from petroleum. …Nylon is still widely used, but, like other plastics, it has environmental downsides: it is made from a nonrenewable resource; its production generates nitrous oxide, a potent greenhouse gas; it doesn’t biodegrade; and it sheds microfibers that end up in food, water, plants, animals, and even the clouds.  Now, however, a San Diego-based company called Genomatica is offering an alternative: a so-called plant-based nylon made through biosynthesis, in which a genetically engineered microorganism ferments plant sugars to create a chemical intermediate that can be turned into nylon-6 polymer chips, and then textiles.   …Using living organisms to create safe materials that break down completely in the environment — where they can act as nutrients or feedstock for new growth — is just one example of a burgeoning global movement working toward a so-called bioeconomy.