AUTHOR=Sharma Chhavi , Timorshina Svetlana , Osmolovskiy Alexander , Misri Jyoti , Singh Rajni 

TITLE=Chicken Feather Waste Valorization Into Nutritive Protein Hydrolysate: Role of Novel Thermostable Keratinase From Bacillus pacificus RSA27

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.882902

DOI=10.3389/fmicb.2022.882902

ISSN=1664-302X

ABSTRACT=<p>Microbial keratinases exhibit a momentous role in converting keratin biowastes into exceedingly valuable protein supplements. This study reports a novel, highly stable keratinase from <italic>Bacillus pacificus</italic> RSA27 for the production of pure peptides rich in essential amino acids from chicken feathers. Purified keratinase showed a specific activity of 38.73 U/mg, 2.58-fold purification, and molecular weight of 36 kDa. Kinetic studies using a chicken feather as substrate report <italic>K</italic><sub>m</sub> and <italic>V</italic><sub>max</sub> values of 5.69 mg/ml and 142.40 μg/ml/min, respectively, suggesting significant enzyme-substrate affinity/biocatalysis. Identification and <italic>in silico</italic> structural-functional analysis of keratinase discovered the presence of distinct amino acid residues and their positions. Besides, keratinase possesses a high-affinity calcium-binding site (Asp<sup>128</sup>, Leu<sup>162</sup>, Asn<sup>164</sup>, Ile<sup>166</sup>, and Val<sup>168</sup>) and a catalytic triad of Asp<sup>119</sup>, His<sup>151</sup>, and Ser<sup>308</sup>, known attributes of serine protease (subtilisin family). Furthermore, a scale-up to 5 L fermenter revealed complete feather hydrolysis (94.5%) within 24 h with high activity (789 U/ml) and total amino acid of 153.97 μmol/ml. Finally, cytotoxicity evaluation of protein hydrolysate resulted in negligible cytotoxic effects (1.02%) on the mammalian hepatoblastoma cell line, signifying its potential biotechnological applications.</p>