Isolation and identification of Bacillus natto strains and their antagonism towards Vibrio parahaemolyticus

Nine Bacillus strains were isolated and purified from natto and Bacillus natto preparation.Then six of these strains were identified as Bacillus subtilis natto according to their physiological and biochemical characters.In the first study, agar diffusion method was used to study the antagonism of Bacillus natto's fermentation broth shake cultivated under different temperature (37, 32, 28℃) and fermentation time (12, 24, 36, 48h) towards Vibrio parahaemolyticus.Then, the predominant strain BN-5 was selected to co-culture with Vibrio parahaemolyticus at 28℃, in order to research its effect on the growth of Vibrio parahaemolyticus.The results showed that, the fermentation broth under 37℃ had a significant inhibitory effect and the effect attenuated quickly with reduction of fermentation temperature and prolongation of fermentation time.Bacillus natto could inhibit the growth of Vibrio parahaemolyticus effectively within 24h when the ratio of initial concentration of BN-5 and Vibrio parahaemolyticus not less than 100.