Abstract: A high-yield nattokinase-producing strain, designated as GULR06, was isolated from smoked cured meat produced by local farmers in Zhijin, Guizhou by measuring fibrinolytic activity of the enzyme produced by this strain. The strain GULR06 was identified as Bacillus subtilis based on morphology, physiological and biochemical characteristics, 16S rDNA sequence analysis and phylogenetic analysis. Natto was prepared by solid state fermentation with soybean as the major ingredient, and the changes of biogenic amines during the fermentation process were detected by high performance liquid chromatography (HPLC). The changes of nattokinase activity and biomass were also investigated. The results showed that cadaverine, putrescine, 2-phenethylamine, tryptamine, spermine, tyramine, spermidine and histamine were well separated by HPLC. The method showed good linearity with R2 greater than 0.994 0, and relative standard derivation (RSD) lower than 4%. The total content of biogenic amine during natto fermentation was in the range of 26.47–72.97 mg/kg, which was safe for human body. After fermentation for 54 h, the activity of nattokinase, (5 439.5 ± 149) IU/g, was the highest, the number of viable cells was 13 (lg(CFU/g)), and the total amount of biogenic amines was (56.18 ± 4.94) mg/kg.

Key words: GULR06 strain, isolate, nattokinase, solid state fermentation, biomass, biogenic amines