Biochemical characterization of a surfactant-stable keratinase purified from Proteus vulgaris EMB-14 grown on low-cost f
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ORIGINAL RESEARCH PAPER
Biochemical characterization of a surfactantstable keratinase purified from Proteus vulgaris EMB-14 grown on low-cost feather meal Michael O. Babalola . Adeyemi O. Ayodeji Joshua O. Ajele
. Olufemi S. Bamidele .
Received: 6 December 2019 / Accepted: 25 July 2020 Ó Springer Nature B.V. 2020
Abstract Objectives The bioaccumulation of keratinous wastes from poultry and dairy industries poses a danger of instability to the biosphere due to resistance to common proteolysis and as such, microbial- and enzyme-mediated biodegradation are discussed. Results In submerged fermentation medium, Proteus vulgaris EMB-14 utilized and efficiently degraded feather, fur and scales by secreting exogenous keratinase. The keratinase was purified 14-fold as a monomeric 49 kDa by DEAE-Sephadex A-50 anion exchange and Sephadex G-100 size-exclusion chromatography. It exhibited optimum activity at pH 9.0 and 60 °C and was alkaline thermostable (pH 7.0–11.0), retaining 87% of initial activity after 1 h pre-incubation at 60 °C. The Km and Vmax of the keratinase with keratin azure were respectively 0.283 mg/mL and 0.241 U/mL/min. Activity of P. vulgaris keratinase was stimulated by Ca2?, Mg2?, Zn2?, Na? and maintained in the presence of some denaturing agents, except b-mercaptoethanol while Cu2? and Pb2? showed competitive and non-competitive inhibition with Ki 6.5 mM and 17.5 mM, respectively.
M. O. Babalola A. O. Ayodeji (&) O. S. Bamidele J. O. Ajele Enzymology and Microbial Biotechnology Unit, Department of Biochemistry, The Federal University of Technology, P.M.B. 704, Akure, Nigeria e-mail: [email protected]; [email protected]
Conclusion This purified P. vulgaris keratinase could be surveyed for the biotechnological transformation of bioorganic keratinous wastes into valuable products such as soluble peptides, cosmetics and biodegradable thermoplastics. Keywords Poultry waste Feather Valorization Keratinase Purification Inhibition
Introduction In the face of rising global human population especially in Africa, production and consumption of poultry meat is increasing with concomitant generation of unwanted feather wastes amidst others (Jin et al. 2017). These solid wastes (feathers, nails, hairs, horns and hooves) contain keratin, a fibrous and recalcitrant structural protein (Jaouadi et al. 2010; Lange et al. 2016) resistant to common proteolytic enzymes routinely used industrially. In fact, chicken feathers making up 5 to 7% of the total weight of mature chickens (de Oliveira et al. 2016) contain up to 80 to 90% keratin on dry mass basis (Ghosh et al. 2008). Keratinous substances are degraded by some microorganisms in a process known as keratinolysis by expressing specific keratinolytic enzymes (keratinases), non-specific proteases and some other enzymes. Keratinases [E.C.3.4.21.11] are usually
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serine or metallo alkaline proteases capable of degrading the scleroprotein, keratin (Lee et al. 2004; Bhange et al. 201
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