Structure and Function of Wool Keratin Polypeptide Extracted by Superheated Water

Abstract

Pyrohydrolytic wool keratin polypeptides (PWKPs) were successfully extracted by hydrolyzing waste sheep wool from a tannery with superheated water. The results revealed that the properties of PWKPs varied significantly under different hydrolysis temperatures. At 170°C, the weight average molecular weight and the polydispersion index of the product PWKP-170 were determined to be 1080 ± 71 Daand 1.55 ± 0.04, respectively, which displayed a distribution trend for “equilong chain segments”. Furthermore, the extraction yieldand the repeated water solubility reached 93.5 ± 1.7% and 99.8 ± 0.2%, respectively, and no α-helical structure was found to exist in PWKP-170. Organic element and amino acid analyses for the PWKPs showed that the decrease in sulfur and cysteine content was related to the fracture of disulfide bonds during the hydrolysis process of keratin. Specificity studies indicated that PWKP-170 exhibited a new ultraviolet absorption characteristic at 309 nm, with an antibacterial titer of 11.24 AU/mg against Staphylococcus aureus at a concentration of 1 × 106 CFU/mL, reflecting its potential application value as a keratin polypeptide functional material.