Bacillus sp. CSK2 produced thermostable alkaline keratinase using agro-wastes: keratinolytic enzyme characterization

Nonso E Nnolim,Uchechukwu U Nwodo

doi:10.1186/s12896-020-00659-2

Abstract

BackgroundChicken feathers are the most abundant agro-wastes emanating from the poultry processing farms and present major concerns to environmentalists. Bioutilization of intractable feather wastes for the production of critical proteolytic enzymes is highly attractive from both ecological and biotechnological perspectives. Consequently, physicochemical conditions influencing keratinase production by Bacillus sp. CSK2 on chicken feathers formulation was optimized, and the keratinase was characterized.ResultsThe highest enzyme activity of 1539.09 ± 68.14 U/mL was obtained after 48 h of incubation with optimized conditions consisting of chicken feathers (7.5 g/L), maltose (2.0 g/L), initial fermentation pH (5.0), incubation temperature (30 °C), and agitation speed (200 rpm). The keratinase showed optimal catalytic efficiency at pH 8.0 and a temperature range of 60 °C – 80 °C. The keratinase thermostability was remarkable with a half-life of above 120 min at 70 °C. Keratinase catalytic efficiency was halted by ethylenediaminetetraacetic acid and 1,10-phenanthroline. However, keratinase activity was enhanced by 2-mercaptoethanol, dimethyl sulfoxide, tween-80, but was strongly inhibited by Al3+ and Fe3+. Upon treatment with laundry detergents, the following keratinase residual activities were achieved: 85.19 ± 1.33% (Sunlight), 90.33 ± 5.95% (Surf), 80.16 ± 2.99% (Omo), 99.49 ± 3.11% (Ariel), and 87.19 ± 0.26% (Maq).ConclusionThe remarkable stability of the keratinase with an admixture of organic solvents or laundry detergents portends the industrial and biotechnological significance of the biocatalyst.

Highlights

Chicken feathers are the most abundant agro-wastes emanating from the poultry processing farms and present major concerns to environmentalists
Optimization of physico-chemical process The initial medium pH was varied from 3.0 to 11.0 and results showed that Bacillus sp
The incubation temperature of the fermentation flasks was varied and the results indicated that Bacillus sp

Summary

Introduction

Chicken feathers are the most abundant agro-wastes emanating from the poultry processing farms and present major concerns to environmentalists. Bioutilization of intractable feather wastes for the production of critical proteolytic enzymes is highly attractive from both ecological and biotechnological perspectives. CSK2 on chicken feathers formulation was optimized, and the keratinase was characterized. Keratinases (EC 3.4.21/24/99.11) are inducible proteolytic enzymes that mediate the bioconversion of insoluble keratinous protein into smaller organic molecules including functional peptides and amino acids [1]. Keratinous biomass are generated in significant quantities from commercial slaughterhouses, and poultry and leather processing industries [4]. Avian feathers are generated in large quantities annually, and the trend should be in the upward trajectory as the demand for white meat rises with the ever-growing world population [5].

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