Purification and immobilization of thermostable serine alkaline protease from Bacillus subtilis

A protease producing bacteria was isolated from soil and identified as Bacillus subtilis. Of the 42 isolate screened, isolate S-8 was identified as thermostable alkaline protease producer. The protease was purified by ion exchange chromatography, and showed apparent molecular weight of 19,000 kD and an isoelectric point of 9.0. The enzyme had optimal proteolytic activities over a broad pH range (8-11) and exhibited temperature optimum of 60 oC. The protease was immobilized on tri (4- formyl phenoxy) cyanurate to form Schiff’s base. The native and immobilized protease was used for catalyzing the hydrolysis of proteins in aqueous medium. The immobilized protease exhibited shift in optimal pH from 10 to 10.5 and optimal temperature from 60 oC to 65 oC. The immobilized protease revealed 10-15% increase in thermal stability and retained 70% of its initial activity after 3 cycles.