Influence of Type of Pre-Hair Treatment from Different Types of Animal Sources on the Degree of Hydrolysis of Keratin

Keratin biomaterials have many different advantages over other biomolecules. A number of techniques have been studied to prepare keratin hydrolysates. Many of them use strong reagents and the processes take place under very drastic conditions. The present study focuses on the following aspects: producing keratin hydrolysates from various animal sources; application of various methods for extraction; comparison of the type of treatment over the degree of hydrolysis. Sheep wool samples were used, respectively native and alkaline pre-treated and samples of goat hair, respectively native and enzyme pre-treated. The methods used for the hydrolysis of keratin materials are: 1) by sulfotolysis with sodium pyrosulfate and urea; 2) with thioglycolic acid and 3) with sodium hydroxide. The obtained hydrolysates were characterized by qualitative reactions, spectrophotometric and FTIR analysis. It was found that the samples from one and the same animal source show very different properties and different degrees of hydrolysis. The highest degree of hydrolysis was achieved for the pre-treated samples. It was proved that the method of hydrolysis with NaOH is the most appropriate for sheep wool and to a much greater extent for the alkaline treated wool than for the native. The reducing agent: sodium pyrosulfate and urea is the most appropriate for enzyme pre-treated samples of goat skin. Therefore, pre-treatment of animal hair samples facilitates the hydrolysis process and makes it easier to break disulfide bonds. The disadvantage of proteins, and in particular keratins, is the difference in the structure of macromolecules, which are obtained from different animal sources. Therefore, this requires a specific approach to the hydrolysis of keratin from each individual animal source.