Abstract: An object of the present invention is to provide a method capable of producing a protein fiber in which shrinkage at the time of first contact with moisture after production is more reliably suppressed and generation of crimp is also suppressed. A method for producing a protein fiber according to the present invention includes: a pre-shrinking step of shrinking a protein fibril in a relaxed state after drawing and before being wound; a winding step of winding the protein fibril subjected to the pre-shrinking step to obtain a wound product; and a post-shrinking step of shrinking the protein fibril subjected to the winding step in a relaxed state.

Abstract: An object of the present invention is to provide a method for producing an artificial structural protein fiber having a small diameter and having a stress equal to or higher than that of the related art. A method for producing an artificial structural protein fiber according to the present invention is a method for producing an artificial structural protein fiber by a wet spinning method, the method including a coagulation step of discharging a spinning dope containing an artificial structural protein and an organic solvent from a spinneret into a coagulation liquid to coagulate the artificial structural protein, wherein a bath draft in the coagulation step is more than 0.4 and 20 or less.

Abstract: Disclosed is a method for manufacturing a fibroin solution including a step of forming a slurry containing a solvent-containing dissolving liquid and a fibroin-containing protein powder dispersed in the dissolving liquid by continuously introducing the protein powder to a thin film of the dissolving liquid while flowing the thin film; and a step of forming a fibroin solution by dissolving, in the dissolving liquid, the protein powder in the slurry.

Abstract: An object of the present invention is to provide a method for producing a modified fibroin multifilament excellent in productivity and a multifilament produced by the same. The multifilament of the present invention contains modified fibroin, in which the multifilament has 100 or more constituent single yarns, a coefficient of variation in elastic modulus is 15% or less, a coefficient of variation in strength is 15% or less, and a coefficient of variation in elongation is less than 33%.

Abstract: A production method of a protein composition, the method comprising a step of hydrolyzing an ester group by bringing a raw material composition containing an esterified protein into contact with an acidic or basic medium.

Abstract: The present invention pertains to an artificial hair fiber that includes an artificial fibroin fiber containing a modified fibroin and that expands when being in a wet state and shrinks when being dried after the wet state.