Characterization of keratin hydrolyzates prepared from sheep wool

Abstract

Preparation of keratin hydrolyzates through alkaline-enzymatic hydrolysis was already described earlier. Employment of hydrolyzates in practice requires knowledge of their composition, thermal stability and molecular weight. The aim of this contribution is to determine molecular weight of keratin hydrolyzates (prepared from sheep wool). Molecular weight (Mw) of keratin hydrolyzates was determined by SDS-PAGE (sodium dodecyl sulphate polyacrylamide gel electrophoresis). Selection of hydrolysis conditions allows to prepare hydrolyzates with predominant share of low-molecular fractions (Mw< 10 kDa), intermediate-molecular fractions (Mw≈ 10-50 kDa) or high-molecular fractions (Mw> 70 kDa). Optimal conditions for preparing keratin hydrolyzates are as follows: in 1ststage of hydrolysis, acting on wool with 0.6% KOH at 90 °C for 48 h; in 2ndstage of hydrolysis, adding 1% (w/w) proteolytic enzyme Savinase 6 T and stirring at 40°C for 24 h. Under these conditions, breakdown efficiency is 63% and a hydrolyzate is prepared containing 11.5% N, 14.9% ash, 2.58% sulphur and a high portion of intermediate- and high-molecular fractions which is comparable in quality to technical gelatine. Keratin hydrolyzate can be employed, for example, to produce wrapping materials (films, coatings, encapsulates).