Protease production by the keratinolytic Bacillus sp. CL18 through feather bioprocessing

Abstract

Bacillus sp. CL18 was investigated to propose a bioprocess for protease production using feathers as organic substrate. In feather broth (FB), containing feathers as sole organic substrate (1-100gl-1), maximal protease production was observed at 30gl-1 (FB30) after 6days of cultivation, whereas increased feather concentrations negatively affected protease production and feather degradation. Protease production peaks were always observed earlier during cultivations than maximal feather degradation. In FB30, 80% of initial feathers mass were degraded after 7days. Addition of glucose, sucrose, starch, yeast extract (2gl-1), CaCl2, or MgCl2 (10mmoll-1) to FB30 decreased protease production and feather degradation. FB30 supplementation with NH4Cl (1gl-1) resulted in less apparent negative effects on protease production, whereas peptone (2gl-1) increased protease yields earlier during cultivations (3days). Through a central composite design employed to investigate the effects of peptone and NH4Cl (0.5-4.5gl-1) on protease production and feather degradation, FB30 supplementation with peptone and NH4Cl (0.5-1.1gl-1) increased protease production within a shorter cultivation time (5days) and hastened complete feather degradation (6days). Feather bioconversion concurs with sustainable production of value-added products.