Purification and characterisation of an acid protease from Aspergillus carbonarius Francis. S. Ire1*, Bartholomew. N. Okolo2 and Anene. A. Moneke2 1
Department of Microbiology, University of Port Harcourt, Port Harcourt, Nigeria 2 Department of Microbiology, University of Nigeria, Nsukka, Nigeria. Accepted 26 September, 2011
The aim of this study is to purify and characterize an acid protease from Aspergillus carbonarius. The protease was purified to apparent homogeneity by 4M sucrose concentration, ion-exchange chromatography on Q-Sepharose, hydrophobic interaction chromatography on Phenyl Sepharose CL4B and gel filtration chromatography through Sephadex G-100. A 10-fold purification with specific activity of 485.47 Umg-1 protein was achieved. SDS-PAGE and zymogram analysis of the protease indicated an estimated molecular mass of 72 kDa. The optimum temperature and pH for the proteolytic activity were 40°C and pH 3.0, respectively. The enzyme was active over a wide range of temperature from 40 to 80°C. The enzyme retained about 70% of its original activity (40°C) at 90 and 100°C.The enzyme was most stable at pH of 3.0 and temperature of 50°C. The enzyme has a relatively broad pH range of 4.0 to 10.0 after 30 min. The enzyme was slightly significantly (P < 0.001) stimulated by K+, Ba2+ 2+ 2+ 2+ 2+ 2+ while Ca and Zn moderately enhanced it. Mn , Fe and Cu strongly significantly (p
