Thermostable keratinase from Bacillus cereus L10: optimization and some potential biotechnological applications

Abstract

AbstractThe accumulation of feather waste is a critical problem in solid waste management; therefore, microbial management of waste is highly significant. Consequently, the keratinolytic capacity of some bacteria isolated from the keratinous waste area was evaluated. The most promising isolate coded as L10 showed the highest feather degradation efficiency 72.7% was identified as Bacillus cereus L10 using 16S rRNA gene sequencing. The effect and contribution of independent process variables were studied by Plackett–Burman design. The optimal values of the independent variables obtained from the Plackett–Burman design were chicken feather, 1%; K2HPO4, 0.3%; KH2PO4, 0.05%; MgSO4 7H2O, 0.01%; yeast extract, 0.05%; inoculum size 4% with pH 7 and incubation period 5 days at 35 °C. The optimal parameters were validated resulting in the enhancement of keratinase production (9.602 U/ml), protein concentration (521.17 µg/ml), and feather degradation (94%) along with a 4.56-fold increased of keratinase production. The enzyme is relatively thermostable, completely stable between 30 and 80 °C for 1 h and retained 97.66% of its activity at 100 °C. B. cereus L10 was able to degrade different types of keratins. Interestingly, the feather hydrolysate from optimized keratinase production medium showed plant growth promoting activity by producing indole-3-acetic acid (IAA). The feathers hydrolysate produced a great benefit by its use as a soil biofertilizer through enhancing the germination of Triticum aestivum. The important implication of keratinase in laundry detergent and leather industry was examined. Results revealed that the enzyme achieved great efficiency in removing protein and blood-rich stains within 30 min at 36 °C in addition to its thoroughly dehairing of cow-hide after 40 h incubation without any damage. The dehaired pelt exhibited a smooth, velvety, and white color surface, good flexibility. Therefore, our study presents an effective method to turn waste into wealth. Graphical Abstract