Screening of high-yield fibrinolytic enzyme-producing strains from traditional fermented douchi (Honghe, Yunnan) and analysis of the gene encoding the fibrinolytic enzyme

High-yield fibrinolytic enzyme-producing bacterial strains were isolated and screened from traditionally fermented douchi from Honghe, by a two-step screening method, in which skim milk agar and fibrin agar were used. The bacterial gene encoding the fibrinolytic enzyme was cloned and analyzed to provide bacterial reference strains and a theoretical basis to develop a new version of functional douchi. Using these methods, a high-yield fibrinolytic enzyme-producing strain Bacillus subtilis LC-2-1 was successfully isolated, which secreted a kind of douchi fibrinolytic enzyme. The molecular mass of the enzyme was 27.4 kDa that contained 275 amino acids encoded by 825 bp. Compared to other douchi fibrinolytic enzymes and nattokinase, the enzyme produced by B. subtilis LC-2-1 showed significant differences, and the amino acid sequence homology was 85.1%. Additionally, the enzyme had high fibrinolytic activity, which was up to 79.84 U/mL. Thus, these results could provide a bacterial reference strain and theoretical basis to develop a new version of fermented douchi with thrombolytic activity.