“…Their efficiency can be evaluated by measuring the enzymic activity, the concentration of both the released thiol groups and soluble proteins, and the incurred weight loss [ 8 ]. 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 ].…”