The same way they turn it into a solid for cheese, only more so,
A LOT of yarns involve turning liquids into solids, including silk, rayon, acrylic.
Most of the new fibers not only involve turning a liquid into a solid, but they FIRST turn solids source material into liquids.
This would include your bamboo, soy, corn, etc yarns.
MMario - *REAL* men knit LACE