Study On Fibrinolytic Dou-chi Fermentation And Its Antioxidative Properties

Six strains of bacillus with fibrinolytic activity were isolated from the traditional Chinese Dou-chi collected in different regions around China. A strongly fibrinolytic enzyme producing strain named DC-1 with the highest enzyme producing ability was screened by means of the improved medium-fibrin plate screening, solid-state fermentation rescreening as well as the morphological and biochemical character identification. After adding carbon source, medium sterilization and inoculation, DC-1 strain was fermented in the solid medium through shallow-plate fermentation technique under the specific condition. Using single-factor test and responsed surface methodology, parameters in fermentation process were analyzed and optimized. The optimal parameters were attained as follows: soybean water content 74%, fermentation time 72h, fermentation temperature 39℃. The maximum enzyme activity under the optimal condition was up to 1130.03IU/mL.Dou-chi fermented with DC-1 strain was extracted in 95% ethanol-water solution for 24 hours. The solution was filtrated, freeze-dried and the dry extract was produced which was then dissolved in 95% ethanol-water solution in order to perform the antioxidative tests. Study showed that Dou-chi dry extract had a strong antioxidative ability, the content of phenolic compounds was as high as 751.03±5.06 mg/g dry extract. Study also suggested that there was a correlation between antioxidative activity and phenolic compounds in Dou-chi extract. In addition, Dou-chi dry extract has a strong ability to scavenge free radicals like [DPPH·] and [·OH].By means of HS-SPME and GC-MS technique, the flavor compounds in Dou-chi sample was analyzed and 46 different volatile compounds were separated respectively, including 12 categories like alcohol, acids, esters, aldehydes, ketones, phenols, pyrazines, and miscellaneous compounds, etc. Pyrazines compounds in particular, as one of the characteristic products formed by Maillard reaction, may play an important role in formations of primary aromas of Dou-chi products.