Spiders make very strong silk, and researchers have long sought to duplicate its structure to make super-strong fabrics that can be used for a wide range of applications — even bullet-proof vests.
Now a leading authority on spider genes says inserting them into alfalfa plants may be the best option for producing the unique protein on a large scale. Molecular biologist Randy Lewis and his team of University of Wyoming researchers have isolated the silk-making gene, successfully transferring it into alfalfa.
They began by working with goats, placing the spider-silk gene into a goat genome, where the protein can be extracted from the milk and spun into fiber.
“The biggest challenge here is producing the protein in a high-enough volume to make it commercially viable,” says Lewis. “It currently takes about 600 lbs of goat milk to produce enough silk to make one bullet-proof vest.”
Transferring the gene into plants seems more practical, he says, and alfalfa offers several advantages.
“First, alfalfa produces more protein than most plants, which should make yields of the spider-silk protein higher as well. Second, alfalfa has a higher percent of larger proteins by weight than most other plants, which is more desirable. And third, there already is a good infrastructure in place for growing, harvesting and transporting the crop.”
A fourth benefit, he adds, may be that the fairly simple process of removing the protein from the crop could be the first part of processing.
“I think it could fit well with processing the crop for ethanol,” he says. “We remove only the protein, which leaves the bulk of the crop behind. Our first step would contribute a second value-added use for the same crop. And if not used for ethanol, what remains could certainly be dried for feed.”
So far, Lewis and colleagues have transferred the spider-silk gene into alfalfa and crossed it with a commonly grown variety, getting expression of the gene 14% of the time.
“Obviously, we need to work to improve that number,” he says. “Once we reach a higher level of expression, we can begin to do variety tests and crosses.”
He predicts that alfalfa containing the gene could be commercially available in 10 years. He's applying for a USDA grant, which could speed the work. When genetic transfer is involved, regulatory agencies look very closely at all aspects of the process, and that can take a long time.
“But here again, alfalfa offers several advantages,” says Lewis. “It doesn't have any wild relatives, so it can't cross-pollinate with another crop, and to be positive about that you'd simply cut the crop before it blooms. Our process does not involve selective advantage like with the Roundup Ready trait, and the protein we'd be producing is non-allergenic, so it wouldn't cause a human threat.”
There are many potential uses for this type of fiber, he says. One medical application being studied is to use it as sutures and scaffolding to repair and regenerate human tendons and ligaments.
“It's strength and ability to absorb energy would make it ideal for use in airbags. It could also be used to coat and stabilize things,” says Lewis. “Anywhere Kevlar is now used, this product could replace it and provide a non-petroleum-based alternative. The number of potential markets for this material is huge.”