Keratinolytic Enzyme Production and Poultry Feather Biodegradation by Bacteria Isolated from Extreme Environments in Botswana

Environmental pollution by hard-to-degrade polymers is on a steep rise and impacting the entire ecosystem. Microbial keratinases are pivotal in the breakdown of protein polymers that are otherwise resistant to most proteases. In this study, we isolated and identified bacteria from Sua pan soil through morphological, biochemical, and 16SrRNA sequencing approaches and further assessed these isolates for their keratinase production potential. Among the screened isolates, four bacteria, Bacillus cereus Bac 2, Bacillus sp. Bac 1, Pseudomonas aeruginosa Bac 3, and Achromobacter insuavis Bac 4, exhibited the highest degradation activity. B. cereus Bac 2 produced the widest clearance zone, whereas A. insuavis Bac 4 produced the narrowest clearance zone on feather meal agar. Protein bands observed in SDS-PAGE gels for the selected isolates further supported the presence of keratinolytic enzymes. We also investigated the effect of temperature and pH on keratinase activity and determined that all the keratinases were alkaline proteases, with B. cereus Bac 2, P. aeruginosa Bac 3, and Bacillus sp. Bac 1 showing maximum activity at a pH of 8.5, while A. insuavis Bac 4 had maximal activity at a pH of 8.0. Overall, our results indicated that B. cereus Bac 2 keratinase had significantly higher activity across all temperature and pH ranges investigated, compared to all the other isolates (p ≤ 0.0001). These findings highlight the potential application of bacterial isolates from alkalophilic environments, in the eco-friendly degradation of feather waste, as valuable by-products such as organic fertilizers, peptides, and amino acids.