Biodegradation of keratin in mineral-based feather medium by thermophilic strains of a new Coprinopsis sp.

Abstract

The disposal of poultry feather waste is a global environmental problem, so degradation of this waste by microbial or enzymatic, environmentally friendly, means is therefore of significant interest. Considering the high protein content of keratin wastes and their great potential as a source of protein or amino acids, degradation of feather was performed by three strains of a novel thermophilic Coprinopsis sp. The strains grew in a mineral-based medium in which chicken feather was the sole source of carbon and nitrogen, where they decomposed the defatted and powdered feather meal into soluble amino acids fractions. Effective protease productivity was observed following 14, 21, 28 and 35 days of incubation and showed a gradual release of soluble amino acids into the medium, corresponding to a decrease in the dry weight of the substrate. The optimal extracellular cell-free keratinase activity was 32 KU/ml expressed in filtrates of 14-day-old cultures, and the optimal cell-bound keratinase activity was 39.9 KU/ml, expressed in centrifuged 21-day-old mats. All strains expressed optimal keratinase activities at 20.40 °C and pH 9.