Rhodococcus erythropolis, Geobacillus stearothermophilus and two Bacillus species (Bacillus pumilis, and Bacillus licheniformis) were evaluated for protease production using feathers as the sole carbon and nitrogen source. The B. licheniformis produced enzymes optimally at 40 degrees C and pH 10.0, while B. pumilis performed optimally at 37 degrees C and pH 7.0. Furthermore, the optimum conditions for enzyme production by G. stearothermophilus were 55 degrees C and pH 7.0-8.0, while for R. erythropolis they were 37 degrees C and pH 7.0. The maximum proteolytic activities of the protease produced by B. licheniformis, G. stearothermophylus and B. pumilis were 50.41, 9.91 and 35.41 U/m1 after 48, 72 and 48h of culture, respectively. With R. erythropolis, the maximum enzyme activity was 33.39 U/ml after 96 h of culture. Also, the production of soluble protein showed the same pattern as that of proteolytic protease. When the initial pH value was 10.0, culturing the feathers (30 g l(-1)) for four days at 40 degrees C resulted in the maximum production of soluble proteins (8.28 mg/ml) by B. licheniformis. These results suggest that new strategies for waste management have emerged after the introduction of keratinases in sustainable material development, which has industrials applications in green technologies. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.