Abstract:

As an extension of our previous fermentation experiments in shake flasks, the objective of this study was tooptimize the fermentation conditions for the production of fibrinolytic enzyme by Bacillus amyloliquefaciens GZJSI-12-7 ina 19 L fermenter. The results showed that plasmin activity began to appear after incubation for 6 h and remained constantafter 78 h at a level of 4 178.39 IU/mL. The peak of enzyme production occurred about 12 h earlier than in shake flasks.Fibrinolytic enzyme was purified from the fermented liquid medium by bactofugation, ammonium sulfate precipitation,dialysis and Sephadex G-75 gel filtration, with a purification fold of 9.84 and an activity recovery of 42.52%. The specificactivity of the purified fibrinolytic enzyme was 48 073.193 IU/mg. Enzymatic characterization showed that the molecularweight of the fibrinolytic enzyme was about 30.2 kD, and its optimum temperature and pH were 40 ℃ and 7.5, respectively.The purified fibrinolytic enzyme was stable blow 40 ℃ but sharply decreased above 50 ℃. The enzymatic activity wasmarkedly catalyzed by Mg2+, Ca2+ and Mn2+, but strongly inhibited by Cu2+ and Fe3+.

Key words: Bacillus amyloliquefaciens, fibrinolytic enzyme, fermentation, purification, characterization