ISOLATION, CHARACTERIZATION AND OPTIMIZATION OF THERMOSTABLE METALLO-KERATINOLYTIC PROTEASE FROM HUMAN HAIR-DEGRADING ASPERGILLUS NIGER STRAIN ND44

Keratinases of microbial origin are a group of protease enzymes with specific characteristic feature of proteolytic cleavage of keratin resulting in the generation of soluble peptides and free amino acids. They play important roles in conversion of world richest proteinous solid-waste‘’ keratinaceous waste’’ into value-added products. This current research work aimed at isolation, purification, characterization and optimization of keratinase isolate from Aspergillus niger Strain (ND44) obtained from human hair macerated in salt medium, for its enzymatic properties in the degradation of trichocytic α-keratin(a fibrous structural protein that resist most proteases degradation based on its stabilized intra-molecular disulphide and hydrogen bonding), while gene sequencing and phylogenetic tree gave expanded details on the structural identity of the isolated Aspergillus niger Strain (ND44). High keratinolytic activity exhibited by this microbial keratinase at high temperature up to 90⁰C confirms it as a hyperthermophilic enzyme, with non-optimums pH peaks at 5.5 and 9.00that spread across both acidic and alkaline regions. The optimum pH, temperature and best co-factors for this human hair keratinase activities obtained via quantification of liberated soluble peptides/proteins using Lowry method; and liberated free amino acids from keratin using Ninhydrin methods were found to be at pH {(12.5) and (12.5)}, temperature {(90 °C) and (60 °C)} and co-factors {(Ni²⁺and Co²⁺) and (Cu²⁺and Ni²⁺)} respectively. The optima percentage degree of human hair degradation and incubation period were found to be 60% in 14 days. The molecular size of Keratinase produced by Aspergillus niger strain (ND44) was about the size of 600bp (0.6Kb).