Identification and Analysis of a Nattokinase-producing Strain Identification of BSNK-5 and Optimization of the Fermentation Conditions Screening of Strains with the High Activity and Thermostability Nattokinase by 60Co γ-ray Irradiation Research of Transferred Synthetic Nattokinase Gene in Tobacco Genome Screening of Nattokinase Producing Strain and Characterazation of Nattokinase