From waste to wealth: the current landscape and future potential in transforming poultry feathers into value-added products

SUMMARYFeathers, mostly made up of keratin protein, constitute significant waste generated during poultry production. Feathers are an inexpensively available, sustainable source of keratin protein. Keratin is a hydrophilic, non-burning and biodegradable biomaterial that could be used to harvest valuable nutrients and protein for food, feed, packaging and non-feed purposes. The majority of this is inefficiently disposed of as incineration and landfilling, thereby leading to environmental pollution. The high cystine content and serine, as well as non-covalent interactions (such as hydrogen bonds, electrostatic forces and hydrophobic forces) and covalent interactions (disulphide bonds), make the polypeptide chain supercoiled and resistant to common hydrolysis or proteolytic action. Traditionally, the hydrolysis of feathers is done by using strong alkalis, acids, or enzymatic action to obtain amino acids. These processes are highly energy-intensive, generate toxic compounds and generate huge amounts of waste; in addition, they negatively affect the quality of end products. The application of microbial keratinase could be an effective but slow process that needs to be combined with other methods to achieve fast degradation. To alleviate these concerns, various novel approaches have been used in the hydrolysis of feathers, such as superheated water and steam flash explosion, ultrasonication and microwave-assisted chemical hydrolysis. The present review critically analysed the current status of the valorisation of feathers into value-added products and the application of novel technologies in improving the process efficiency.