Unlocking the Keratinolytic Potential of Brevibacillus agri Derived Keratinase: A Molecular Characterization Study

Keratinases have an established role in degrading highly stable and insoluble fibers of keratin proteins, which are otherwise difficult to be hydrolyzed by conventional proteases. Keratinases find promising application in degrading poultry waste to valuable products. Moreover, their role in cosmetics, detergents, agriculture and the leather industry is well recognized.

In this study, the keratinase gene from locally isolated Brevibacillus agri bacteria was cloned and expressed in Escherichia coli, and some of its potential applications were explored.

1300 bp amplified gene from Brevibacillus agri was cloned into E. coli DH5α competent cells using pTZ57R/T vector. After blue-white screening, the positive clone was confirmed by colony PCR and restriction analysis. Purified keratinase gene KerH from recombinant pTZR/KerH plasmid was ligated into pET-28a (+) and transferred into competent cells of E. coli DH5α. Following confirmation through colony PCR, and restriction analysis, recombinant plasmid (pET-28a/Ker) from the positive clone was transferred into competent E. coli BL21 cells. The transformed cells were then cultured for up to 8 hours after induction with 0.8 mM IPTG and lysed by sonication. The resulting recombinant keratinase (KerH) was purified by heat treatment and Ni-affinity column and characterized.

The blast analysis and homologous sequences in the NCBI database established a close link to Brevibacillus agri. The highest expression from transformed E. coli BL21 was achieved with 0.8 mM IPTG following 6 hours of induction. The resulting recombinant keratinase (KerH), purified by Ni-affinity chromatography, possessed 283 U/mg specific activity and displayed ~45 kDa band on SDS-PAGE and zymogram. Secondary structure analysis and active site prediction was performed computationally. Considering the extensive applications of keratinase, KerH was found to be useful in dehairing animal skin surfaces without any damage. The encapsulated KerH possessed improved stability and better compatibility with commercial detergents. It efficiently removed blood, turmeric, strawberry, and egg yolk stains from the fabric. Furthermore, KerH significantly degraded the poultry feathers and provided a protein hydrolysate that helped in converting damaged, dull and curly hair into healthier, shiny and straightened hair.

These key findings highlight that KerH is a robust keratinase with significant potential as an environmental-friendly alternative to the prevailing harsh chemical treatments in various industries. Encapsulation enhanced its suitability by improving its stability and shelf-life. Its broader substrate specificity, stability and application in detergents and cosmetics underline its commercial importance.

The recombinant KerH from Brevibacillus agri can be considered as a valuable microbial keratinase that can be used as an alternative to the eco hazardous chemicals used in commercial applications of feather degradation, hair protein treatment, feather keratin hydrolysate production and hide dehairing.