Silk
Silk moths lay eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed fresh mulberry leaves. After about 35 days and 4 moltings, the caterpillars are 10,000 times heavier than when hatched and are ready to begin spinning a cocoon. A straw frame is placed over the tray of caterpillars, and each caterpillar begins spinning a cocoon by moving its head in a pattern. Two glands produce liquid silk and force it through openings in the head called spinnerets. Liquid silk is coated in sericin, a water-soluble protective gum, and solidifies on contact with the air. Within 2–3 days, the caterpillar spins about 1 mile of filament and is completely encased in a cocoon. The silk farmers then heat the cocoons to kill them, leaving some to metamorphose into moths to breed the next generation of caterpillars. Harvested cocoons are then soaked in boiling water to soften the sericin holding the silk fibers together in a cocoon shape. The fibers are then unwound to produce a continuous thread. Since a single thread is too fine and fragile for commercial use, anywhere from three to ten strands are spun together to form a single thread of silk.
Kraig Biocraft Laboratories
The method used to genetically modify the silkworm uses the PiggyBac Transposon vector discovered and developed by Dr. Fraser at the University of Notre Dame. Specific sequences of spider silk DNA are inserted into the genetic makeup of the silkworm to create a strain of the insect that now produces the spider protein. They are able to customize the sequences that are inserted into the silkworm, thus giving the ability to customize the resulting silkworm's thread strength and flexibility. To ensure the silkworm has been genetically modified, a gene was attached that gave the transgenic silkworms red glowing eyes.
The thread produced by the transgenic silkworms is close to the strength and flexibility of the native spider. Strength relative to native spider silk is 80%. Kraig Biocraft Laboratories is not the first to create transgenic silkworms incorporating spider silk proteins. Where Kraig Labs has succeeded is that the spider silk proteins are integrated structurally into the transgenic silkworm fiber.