Disclosed herein are novel keratin fibers, including, for instance, high-tenacity keratin fibers and high-tenacity keratin composite continuous fibers, and methods for the production and use thereof. A method of producing keratin fibers includes one or more of: (1) using a keratin solution having at least about 65% keratin, which may also have one or more anti-plasticizing agents, (2) extruding a keratin solution into a solution bath, (3) drawing one or more keratin fibers through a solution bath (e.g., at a draw ratio of at least about 110%), and/or (4) drawing one or more keratin fibers through one or more heated environments. High-tenacity keratin fibers disclosed herein may have one or more of the following properties: (1) a keratin content of at least about 65%, (2) a thickness of less than about 40 m, (3) a tenacity greater than about 15 cN/tex, and (4) being biocompatible.

Disclosed is a method for producing a protein fiber, the method including: bringing a spinning dope containing a protein and an organic solvent into contact with a coagulation liquid to coagulate the protein, wherein a content of the protein in the spinning dope is more than 10% by mass based on a total amount of the spinning dope, and the coagulation liquid contains water or an aqueous solution of pH 0.25 or more and pH 10.00 or less.