Study On The Optimal Fermentation Condition And Stability Of Bacteriocin Produced By Bacillus Subtilis A32

The optimation of bacteriocin produced by Bacillus subtilis A32was mainly studied in this test. The optimum fermentation culture medium of the bacteriocin was obtained by single factor experiment. The optimum fermentation condition of bacteriocin produced by Bacillus subtilis A32was obtained systematically through the response surface method based on single factor experiment. The titer of this bacteriocin was determined by using the double dilution method. There was also the study on heat stability, pH stability, metalion stability and surfactant stability of bacteriocin produced by Bacillus subtilis A32. The main results were as follows:1.The optimal fermentation culture medium was1g beef extract,2g soya peptone,0.5g NaCl,0.1g polyethylene glycol6000,0.15gMgSO4and0.04mol/L citrate buffer of100mL.2.The optimal fermentation condition obtained by applying response surface design was fermentation time30h, Table speed147r/min, fermentation pH5.3.3.The bacteriocin titer was increased100%than the original fermentation condition by double dilution determination method.4.The results showed that heat stability and pH stability of the bacteriocin were very good. The activity was still high after the heating at50～90℃.There was48%activity left after heating at100℃for15min. The activity of this bacteriocin was almost no change between pH6and pH9.When pH was5and10, the activity was still90%of original value. When the pH<5or pH>10, the bacteriostatic activity declined significantly. And there was still47%activity left when pH=2. Fe2+Mg2+Ca2+Zn2+could enhanced the inhibitory effect, but effect of Al3+K+Cu2+Na+was adverse. The stability of this bacteriocin of polyethylene glycol6000,twain20and twain80was also good.