| Natto is a kind of fermented food with a variety of nutrition and health functions. Nattokinaset can dissolve the thrombus and reduce blood pressure, and it is now widely promoted in the market. Natto has inhibition against a variety of bacteria, but the report about purified antimicrobial substance has not been published. This paper studied on the optimum producing process, nutrition of natto, separation and purification of protein and its antibacterial action.The production process of the natto was established, including the mass of water added in the soybean, the time of soaking, cooking temperature and time, then the amount of strain, pavement thickness, culturing temperature and relative humidity and after-ripening. The results showed that:3times mass of water was added into soybeans, which was soaked for12h, steamed for7mins at121℃and cooled. Then10ml water and0.2g Bacillus natto powder was added into soybeans (Bacillus natto powder/soybeans:0.2%, w/w%), then the mixture was paved as3cm thickness. The soybeans were cultured at39℃,80%relative humidity for24h. Then the fermented soybeans were placed into refrigerator for4days at4℃, and high-quality natto production was obtained.The protein extracted from produced natto has strong antibacterial activities against E. coli, Salmonella and Staphylococcus aureus. With the increasing of the protein concentration, the diameters of inhibition zone get larger; heated by short-term high-temperature or for long time, the diameters of inhibition zone changed little; with lower concentration of indicator bacteria, the diameters of inhibition zone get greater.Molecular weight of the protein extracted was analyzed by SDS-PAGE. And molecular weight of the protein extracted was from14.4to104.4kDa, and protein with molecular weight41.4kDa,51.0kDa,63.5KDa,81.3kDa and104.4kDa were most abundant; protein was separated by Sephadex G-100, then protein in the5、6and7tubes had bigger absorbance and obvious bacteriostatic action. |
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