A Review: Valorization of Keratinous Materials

Purpose The aim of the present work was to discuss the current state-of-the-art in the methods of utilization of keratinous materials. Various approaches were discussed—thermal, physical, chemical and biological. Results Keratinous wastes can be used as the feedstock, however processing is required to valorize the waste. Among the processing methods, several hydrolytic technologies can be mentioned: hydrothermal methods, enzymatic hydrolysis, bioconversion. Chemical hydrolysis requires the step of neutralization and some nutritive amino acids are lost. Among hydrothermal methods which require high temperature and pressure conditions, acidic hydrolysis assures more complete degradation of keratin than basic. The obtained product can be used as low-quality livestock feed. Another method to obtain solubilized keratin is degradation by lime. More advantageous are enzymatic and bioconversion methods which assure milder conditions and preserve nutritional properties of the produced meal. Conclusions The hydrolyzate can be used as the source of amino acids and peptides in the production of feeds and fertilizers.