Identification and characterisation of a Bacillus licheniformis strain with profound keratinase activity for degradation of melanised feather

摘要

Significant amount of keratins in the form of feather, hair, hoof and horn are generated annually by the livestock industry. Keratinases are increasingly important in the reprocessing and environmental pollution control of keratin wastes. The aim of this study is to isolate a microbial strain of high keratinase activity and to evaluate its feather degrading potential. Thirty-two keratin degrading microbial strains from farmyard wastes and primary effluent were isolated using a selective medium containing feather meal at 30, 37 and 50 °C. One of the isolates, which demonstrated the highest keratinolytic activity (11.00 ± 0.71 Uml-1) was identified as a species of Bacillus licheniformis based on the 16S rDNA analysis, designated as strain N22 and deposited in a culture collection. Optimum keratinase production by this bacterium was achieved in 32 h using a minimum growth medium containing 1.1% (w/v) feather meal at 50 °C and pH 8.5. The molecular weight of the keratinase was ≈ 28 KDa as determined sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis and confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The keratinase reported here significantly degraded melanised feather in 48 h in the absence of reducing agents. There are few reports on the evaluation of feather degrading ability of keratinases using highly resistant melanised feather. The efficient degradation of melanised feathers by this keratinase may offer an environmentally friendly solution to the degradation of feather waste and other organic matter of similar molecular composition.