Thermoactive metallo-keratinase from Bacillus sp. NFH5: Characterization, structural elucidation, and potential application as detergent additive

Lupho Kokwe; Nonso E Nnolim; Lewis I Ezeogu; Bruce Sithole; Uchechukwu U Nwodo

doi:10.1016/j.heliyon.2023.e13635

Thermoactive metallo-keratinase from Bacillus sp. NFH5: Characterization, structural elucidation, and potential application as detergent additive

Heliyon. 2023 Feb 13;9(2):e13635. doi: 10.1016/j.heliyon.2023.e13635. eCollection 2023 Feb.

Authors

Lupho Kokwe^{1

2}, Nonso E Nnolim^{1

2}, Lewis I Ezeogu³, Bruce Sithole⁴, Uchechukwu U Nwodo^{1

2}

Affiliations

¹ SAMRC Microbial Water Quality Monitoring Centre, University of Fort Hare, Alice, Private Bag X1314, 5700, South Africa.
² Applied and Environmental Microbiology Research Group (AEMREG), Department of Biochemistry and Microbiology, University of Fort Hare, Alice, 5700, South Africa.
³ Department of Microbiology, Faculty of Biological Sciences, University of Nigeria, Nsukka, Nigeria.
⁴ The Biorefinery Industry Development Facility, Chemicals Cluster, Council for Scientific and Industrial Research, 359 Mazisi Kunene Road, 4001, Glenwood, Durban, South Africa.

Abstract

In recent times, robust green technological developments have advanced the goal of a circular economy by minimizing waste generation. The study was undertaken to explore the keratinolytic activity of chicken feather-degrading bacteria from South African soil. Isolates coded as SSN-01 and HSN-01 were identified as Bacillus sp. NFH5 and Bacillus sp. FHNM and their sequences were deposited in GenBank, with accession numbers MW165830.1 and MW165831.1, respectively. Extracellular enzyme production and thiol group generation by Bacillus sp. NFH5 peaked at 120 h with 1879.09 ± 88.70 U/mL and 9.49 ± 0.78 mM, respectively. Glutamic acid (4.44%), aspartic acid (3.50%), arginine (3.23%), glycine (2.61%), serine (2.08%), and proline (2.08%) were relatively higher in concentration. Keratinase (KerBAN) activity was highest at pH 8.0 and 90 °C but was inhibited by both EDTA and 1,10-phenanthroline. In addition, the keratinase-encoding gene (kerBAN) accessioned OK033360 had 362 amino acid residues, with molecular weight and theoretical isoelectric point of 39 kDa and 8.81, respectively. Findings from this study highlight the significance of Bacillus sp. NFH5 in the bio-recycling of recalcitrant keratinous wastes to protein hydrolysates - potential dietary supplements for livestock feeds. The properties of KerBAN underscore its application potential in green biotechnological processes.

Keywords: Amino acids; Bio-recycling; Keratinolytic protease; Livestock feed; Protein hydrolysate.