Specialty Fabrics Review October 2019 - 51

Your High Temperature Advantage

Silkworms are genetically modified
by Kraig Biocraft, with spider genes
spliced in to create silk with greater
strength and flexibility. A cocoon used
to produce spider silk is on the right,
while an unmodified cocoon is on the
left (shown under ultraviolet light).
Photo: Kraig Biocraft Laboratories Inc.

on the leaves of the white mulberry tree
to produce those cocoons, Kraig uses
technology-splicing in spider genes-to
make a recombinant silk with strength and
flexibility far exceeding mundane silk.
Kraig has changed the "recipe" for silk
by using genetic modification, according to
Rice, but continues to rely on traditional,
"very ancient processes" to extract the fiber.
That stands in contrast with competing
techniques (or synthetic alternatives)
for spider silk, he says, that use chemicals
and generate greenhouse gases-and are
more expensive.
"We let nature do the work for us," he
says, which reduces the environmental
impact of producing the silk.
The key, says Rice, is changing the
silkworm's DNA, "which took years of
work in the laboratory.
"Our silkworms are happy to go about
their life, and when it comes time to
make silk, they go pull up the recipe page
for silk," says Rice. "But now, instead of
making the silk a traditional silkworm

would make, they start producing this
higher-strength, high-elasticity version
of silk protein."
"We create a parent strain in the lab,
and then the next generations continue to
carry those fiber performance properties
forward," he explains. "Then it's simply
a matter of scaling up the number of
silkworms, generation after generation, to
produce a commercial production platform
for recombinant spider silk."
Not all strains are the same because the
applications require different characteristics.
"We look at ways to impact strength,
elasticity or a combination," Rice explains.
"There are applications where high
strength is good but elasticity isn't." For
example, protective materials produced for
the military, he says, may need superior
strength but low elasticity so they can
absorb an impact without moving.
"It's amazing what we can do with
new genetic engineering tools, but I think
we're just scratching the surface of what's
possible," says Rice. "Our wish list of ideas
and things we're looking to pursue for
spider silk far exceeds our funding at this
point. But as we grow, we'll be able to
explore more interesting approaches."
In some ways, he adds, the textile
market is "low-hanging fruit. We're
starting to look at things like medical
applications. Since spider silk is
biocompatible, it can be great for a medical
suture or other imbedded material. It
doesn't have an interaction with the body.
In fact, Roman soldiers used spider silk as
a wound dressing 2,000 years ago."
Spider silk is produced using a
renewable resource-the mulberry tree-
and is biodegradable, "so it won't sit in
a landfill forever," says Rice.
"But beyond that," he adds, "it just has
incredible performance properties. It goes
far beyond a fancy dress or really great
bulletproof jacket."
Jeff Moravec is a freelance writer
from Minneapolis, Minn.

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