Iron containing keratinolytic metallo-protease produced by Chryseobacterium gleum

Chryseobacterium gleum exhibited complete dissolution of whole chicken-feathers (10 g l−1, pH 8) after 72 h at 30 °C through synthesis of keratinolytic protease when inoculated at 1% (v/v). This enzyme was purified to 67-fold with yield of 2.25% having a specific activity of 1670 U mg−1 and ∼36 kDa Mw. MALDI-TOF MS of this keratinase showed some similarity with the keratinase peptides of Bacillus subtilis (BOFXJ2). The keratinase action was inhibited by EDTA, iodoacetamide and metal ions like mercury, copper and zinc (1 mM each), while it was enhanced by iron and calcium. Keratinase showed presence of 3 mM of Fe M−1 as tested by atomic absorption spectroscopy and addition of Fe in its apoenzyme retained about 79% of original residual feather degradation activity which portrayed it to be metalloprotease. Purified keratinase revealed significant degradation (85%) of feather concentrate (20 g l−1) to 3.9 μM ml−1 of free amino groups in 24 h at an initial pH of 8.0, 30 °C and 120 rpm shaking. This keratinase activity can be controlled precisely by presence of chemical or metal ions which could be of use in biotechnology industry while the culture can be used in poultry waste management.

► Chryseobacterium gleum was evaluated for feather keratin degradation.
► Keratinolytic protease of C. gleum was purified having relative Mw ∼36 kDa.
► Iron found in keratinolytic protease which enhanced its activity.
► Inhibition by EDTA confirmed its class as metallo-protease.