3. Extraction and Characterization of Keratin from Different Biomasses

Keratin is a high-sulphur content protein, highly abundant in nature since it is the major component of feathers, hair, wool, horns and nails. In recent years, keratin-based materials have received great consideration due to its unique features in terms of ability to absorb heavy metals and other toxic compounds, thus resulting particularly useful for water and air purification. Moreover, due to its intrinsic efficacy in promoting cells growth, along with its ability to encapsulate both hydrophobic and hydrophilic drugs, keratin has been increasingly studied for the preparation of a wide range of bio-medical devices, especially in the field of tissue engineering and controlled drug delivery. Extraction of keratin from low-cost biomasses deriving from food industry by-products (especially slaughterhouse, dairy and poultry industry) is a challenging process hampered by the presence of a high content of disulphide bonds that bestow the protein with high resistance to chemical, enzymatic and thermal treatments. Thus, the large-scale use of keratin strongly depends on the development of cost-effective and time-efficient extraction methods. This chapter gives an overview on the availability of different keratinous biomasses and examines the various extraction methods proposed in the literature, underlining their advantages and limitations. Moreover, a detailed comparison between the chemical–physical properties of keratins obtained from different biomasses is here reported.