“They’ve clearly shown that E. coli can make these large proteins, and engineered them to have the resources to do it,” says Randy Lewis, professor of molecular biology at the University of Wyoming. Lewis predicts that it will be possible to use a bacterial system to produce kilogram quantities of artificial spider silk within a few years.
Kaplan says that’s his plan. “We’d like to turn it into a continuous production process,” he says.
Kaplan says what’s needed now are more energy-efficient methods for making the proteins into fibers. Using spinning methods similar to those used to make polymer fibers such as polyester, his group has created fibers from the team’s proteins with properties comparable to natural dragline silk in terms of strength, elasticity, and toughness. However, because spider-silk proteins are finicky and insoluble in water, spinning them into fibers requires high-temperature processing and harsh solvents.
The fibers “take a huge amount of energy to put together,” says Kaplan. Materials scientists would like to make silk fibers the way spiders do: at ambient temperatures, with no harsh solvents.
A novel approach to the problem is being pursued by Luke Lee, director of the molecular nanotechnology center at the University of California, Berkeley. He is designing spinning systems that incorporate microfluidic channels designed to provide the salt- and solvent- gradients found in spider glands. A company called Refactored Materials, founded by students of Lee’s and Voigt’s, is also working on the spinning problem.