A statistical approach for the enhanced production of alkaline protease showing fibrinolytic activity from a newly isolated Gram-negative Bacillus sp. strain AS-S20-I

An alkaline-fibrinolytic protease-producing bacterial strain (AS-S20-I) isolated from a soil sample in Assam was a Gram-negative rod and grown at temperatures ranging from 25 to 55°C, and pH 6.5 to 11.0. Taxonomic identification of isolated strain by polyphasic approach (phenotypic characterization, chemotaxonomic properties, and ribotyping data of the strain) suggested that it belongs to the genus Bacillus, for which the name Bacillus sp. strain AS-S20-I (MTCC 8961) was proposed. The initial screening by using Plackett–Burman's design demonstrated that among the tested factors, casein, ammonium sulphate and pH of the medium significantly (p < 0.05) enhanced the protease (fibrinolytic enzyme) yield in submerged fermentation. Further optimization of fibrinolytic protease production by Bacillus. sp. strain AS-S20-I in SmF by applying RSM was achieved as 749.0 × 103 U L−1 in the presence of 3.0% (w/v) casein and 0.12% (w/v) ammonium sulphate at pH 10.9 and 45°C. This was a 4.0-fold increase in yield compared with that obtained before applying the Plackett–Burman and RSM experimental design. The protease preparation preferentially degraded the fibrin (specific activity 2408.0 ± 70.0 U mg−1; mean ± S.D.) suggesting that its future application in pharmaceutical industry as thrombolytic and anticancer drugs is highly promising.