Keratinases as Versatile Enzymatic Tools for Sustainable Development

Abstract

To reduce anthropological pressure on the environment, the implementation of novel technologies in present and future economies is needed for sustainable development. The food industry, with dairy and meat production in particular, has a significant environmental impact. Global poultry production is one of the fastest-growing meat producing sectors and is connected with the generation of burdensome streams of manure, offal and feather waste. In 2020, the EU alone produced around 3.2 million tonnes of poultry feather waste composed primarily of keratin, a protein biopolymer resistant to conventional proteolytic enzymes. If not managed properly, keratin waste can significantly affect ecosystems, contributing to environmental pollution, and pose a serious hazard to human and livestock health. In this article, the application of keratinolytic enzymes and microorganisms for promising novel keratin waste management methods with generation of new value-added products, such as bioactive peptides, vitamins, prion decontamination agents and biomaterials were reviewed.

Production and characterization of a new detergent-stable keratinase expressed by Pedobacter sp. 3.14.7, a novel Antarctic psychrotolerant keratin-degrading bacterium

“…The aim of our work is to go deeper in the study of Antarctic proteases with keratinolytic activity. This type of enzyme is attractive because it can be applied in various industries, such as leather, textile, chemical, pharmaceutical, food, and nutrition industries, as well as in biotechnology protection [ 42 ].…”

Microbial Pretreatment of Chicken Feather and Its Co-digestion With Rice Husk and Green Grocery Waste for Enhanced Biogas Production

“…Ammonia is linked to the presence of protein sources in the feed. Because CFs are mainly composed of protein, hydrolysis results in ammonia accumulation ( Sypka et al, 2021 ). During AD of the nitrogenous feedstock, ammonia inhibition is one of the main challenges, resulting in lower biogas yield ( Chen et al, 2008 ).…”

“…Feathers are composed of keratin protein, having a recalcitrant structure. The cross-linking and covalent bonds added more strength to the feather’s structure ( Sypka et al, 2021 ). Different pretreatment methods are used like superheated water, strong acids, or alkalis puffing, and pressurized breakdown of feathers ( Chao et al, 2021 ), and many other physiochemical methods could be applied ( Wang et al, 2012 , 2019 ).…”

Valorization of Livestock Keratin Waste: Application in Agricultural Fields

“…Since the cost of keratinase production is high, several researchers have increased the yield and stability of keratinases by altering the genome of keratinolytic organisms via physical and chemical mutagenesis or recombinant DNA technologies [ 80 , 82 , 90 , 93 , 94 , 95 , 96 ]. Keratinases have become increasingly popular, and many studies have reviewed their discovery, production, classification, structure, hydrolysis function, and industrial application [ 9 , 97 , 98 , 99 , 100 ]. Biological techniques are environmentally friendly methods to hydrolyze keratin, but they require more time than other methods.…”

“…The formation of disulfide bonds cross-links the polypeptide chain in keratin, making it insoluble in water, salt solutions, diluted acids, and alkali solutions; these disulfide bonds also confer excellent mechanical resistance. Thus, keratin is resistant to the degradation of commonly used proteolytic enzymes [ 9 ]. Keratins are grouped into hard (feathers, hair, hoofs, and nails) and soft (skin and callus) types, according to their sulfur contents.…”