Fibrinolytic enzyme from newly isolated marine bacterium Bacillus subtilis ICTF-1: Media optimization, purification and characterization

摘要

Fibrinolytic enzymes are important in treatment of cardiovascular diseases. The present work reports isolation, screening and identification of marine cultures for production of fibrinolytic enzymes. A potent fibrinolytic enzyme-producing bacterium was isolated from marine niches and identified as Bacillus subtilis ICTF-1 on the basis of the 16S rRNA gene sequencing and biochemical properties. Further, media optimization using L_(18)-orthogonal array method resulted in enhanced production of fibrinolytic enzyme (8814 U/mL) which was 2.6 fold higher than in unoptimized medium (3420 U/mL). In vitro assays revealed that the enzyme could catalyze blood clot lysis effectively, indicating that this enzyme could be a useful thrombolytic agent A fibrinolytic enzyme was purified from the culture supernatant to homogeneity by three step procedures with a 34.42-fold increase in specific activity and 7.5% recovery. This purified fibrinolytic enzyme had molecular mass of 28 kDa, optimal temperature and pH at 50°C and 9, respectively. It was stable at pH 5.0-11.0 and temperature of 25-37°C. The enzyme activity was activated by Ca~(2+) and obviously inhibited by Zn~(2+), Fe~(3+), Hg~(2+) and PMSF. The purified fibrinolytic enzyme showed high stability towards various surfactants and was relatively stable towards oxidizing agent Considering these properties purified fibrinolytic enzyme also finds potential application in laundry detergents in addition to thrombolytic agent. The gene encoding fibrinolytic enzyme was isolated and its DNA sequence was determined. Compared the full DNA sequence with those in NCBI, it was considered to be a subtilisin like serine-protease.