Collagen and Keratin Hydrolysates as Valuable Additives for Renewable New Products in Circular Economy

Collagen and keratin-based waste represents a valuable biomass resource with still insufficiently exploited potential. The leather industry and sheep breeding activity generate important protein waste based on collagen and keratin which at world level amounts to 5.6 million and 1 million tonnes, respectively, every year. The processing of protein-based waste through water or chemical-enzymatic hydrolysis, allows the refinement of the molecular weights and distribution with different potential functionalities for versatile new products with applications in industry (deliming agents, filling and finishing additives), agriculture, medicine, or other fields. The versatile properties as a function of hydrolysis process were shown by analyses of protein degradation (ATR-FTIR spectroscopy), molecular weight distribution (SDS-PAGE electrophoresis) and particle size distribution (DLS analyses). The specific molecular weight distribution of collagen and keratin hydrolysates after hydrolysis at 100°C and 130°C was highlighted, thus proving the potential of refining the compositions for different applications with ecological impact. The collagen hydrolysis at 100°C leads to fragmentation of large molecules into small molecules meanwhile the temperature of 130°C favors the increase of medium size population of peptides, in agreement with SDS-PAGE electrophoresis results. Instead, the small molecules of keratin were doubled by hydrolysis at 130°C, in good correlation with ATR-FTIR determination of AI/AA ratios.