Abstract

A feather-degrading bacterium Pseudomonas aeruginosa C11 was isolated from feather dumping soil with quick plate screening technology and identified based on morphological and biochemical characterization and analysis of 16S rDNA sequences. The keratinolytic protease from P. aeruginosa C11 was purified 17.4-fold through ammonium sulphate precipitation, a sephadex G-75 gel filtration column and a DEAE sepharose fast-flow column. The purified keratinolytic protease could deeply degrade raw feathers within 24 h at 37°C. The relative molecular mass of the protease was estimated to be 33 kDa by SDS–PAGE. The protease was stable in pH range 5 to 10 and at temperature below 50°C with optimum pH of 7.5 and optimum temperature of 60°C. Mn²⁺ stimulated the keratinolytic activity by 21% at 2 mM, while Co²⁺, Cu²⁺, Zn²⁺, Hg²⁺, Pb²⁺ and Fe²⁺inhibited the keratinolytic activity. The keratinolytic activity was strongly inhibited by EDTA, but not by PMSF, which indicated the protease was a metalloprotease. The isolated protease was different from any reported keratinolytic metalloprotease and was worthy of further investigation.

Key words: feather-degrading bacterium, keratinolytic protease, enzymatic characterization, Pseudomonas aeruginosa.