Purification and characterisation of keratinase from a thermotolerant feather-degrading bacterium

Abstract

Isolation and identification of a thermotolerant feather-degrading bacterial strain from Thai soil as well as purification and properties of its keratinase were investigated. The thermotolerant bacterium was identified as Bacillus licheniformis. The keratinase was purified to homogeneity by three-step chromatography. The purified enzyme exhibited a high specific activity (218 U mg-1) with 86-fold purification and 25% yield. The enzyme was monomeric and had a molecular mass of 35 kDa. The optimum pH and temperature for the enzyme were 8.5 and 60°C, respectively. The enzyme activity was significantly inhibited by PMSF and partly inhibited by EDTA and iodoacetamide, but was stimulated by metal ions. It hydrolysed soluble proteins with a relative activity of 4-100% and insoluble proteins, including keratins, with a relative activity of 3-35%. Therefore, the enzyme could improve the nutritional value of meat- and poultry-processing wastes containing keratins, collagen and gelatin. © Springer 2005.