Micro-filtration Concentration Of Broth And Microencapsulation Of Bacillus Thuringiensis

The membrane technology were applied to innovate traditional downstream processing of Bacillus thuringiensis in the article. Firstly, the working parameters of micro-filtration technology was obtained, and then, we researched the Theological property of the concentrated broths of Bacillus thuringiensis systematically and the effect on the broth properties and spraying dryness by micro-filtration technology. We could conclude that the micro-filtration-spray-drying technology of Bacillus thuringiensis pesticide was better than that of centrifugation—spray-drying. Finally, The microencapsulation of Bacillus thuringiensis was developed to improve the storage prosperity and persistence of the formulation.We found that the micro-filtration membrane permeation flux rapidly decreased in the first 10 minutes and then sustained about 80L·m^-2·h^-1 in a succedent hour. The proper parameter of micro-filtration was attained by the change of the membrane permeation flux in the different operation condtions. The proper operation condition was 0.12 0.14MPa of operation pressure, 40 45℃ of temperature and 4.5 5.0 of pH. The relationship between the viscosity of broth and the membrane permeation flux at different temperature was inverse ratio. So we could infer that the temperature effected on the membrane permeation flux by changing the viscosity of the broth.The rheological behavior of the broth and the concentrated broths of Bacillus thuringiensis was studied at 15 50℃ and rotational speed ranging from 75 to 750 r/min. Flow behavior index of less one confirmed pseudoplasticity (n = 0.7347 0.9748). The power law model well fitted the flow curves of the broth and its concentrates. The consistency coefficient increased with rise in concentration, while the flow behavior index decreased. Two models, η_a = K₀ exp (Ea/RT) and η_a =a exp (b C²) could be used to describe the effect of temperature and concentration on the apparent viscositiy of concentrated broth respectively by regression analysis. And the model η_a = a exp (Ea/RT + bC²) expressing the combined effect of the temperature and concentration on the apparentviscosity was given, which could be used to predict the apparent viscosity of concentratedbroth.The effects of micro-filtration concentration on the spore, crystal protein content, titer and viscosity were studied. After concentration of the fermentation broth, the density, viscosity, solid content, spore, crystal protein content and titer increased, while the titer yield decreased. The broth concentrated by 1.94 times from micro-filtration, the yield rate of parasporal crystal, spore and titer were 87.4%, 100%, and 71.6% respectively, but no papasporal crystal was detected in the infiltration. Concentration by micro-filtration led to the losing of the potentiator, but loss of the titer resulting from micro-filtration was less than that of centrifugalization. The 9-fold concentrated extravasate was able to increase the activity of the micro-filtration concentrated broth by 1.01 times.The titer of the powder from the spray drying of the broth, concentrated broth, broth with filler and concentrated broth with filler are 51347, 56239, 53358, 56209IU/mg respectively, and their quality yield rate are 75.52%, 73.48%, 92.70%, and 72.50%. Some filler could improve the quality yield rate, but the filler had no obvious effect on the concentrated broth with high concentration.The best condition of complex coacervation was obtained by the orthogonal experiment. And the microencapsultion of Bacillus thuringiensis was made on the basis of it. The microencapsulation of Bacillus thuringiensis was found to have better ability of anti-ultraviolet radition than powder. After treated by Ultraviolet 8 hours the titer of the microencapsulations of Bacillus thuringiensis increased from by 4.6% to by 43.2%, but decreased by 40.3% that of powder; the livability of the spore of the microencapsulations varied from 56.0% to 96.8%,but only 5.7% that of powder. The titer loss percent of microencapsulated formulation after speedup reservation (54 ± 2°C, 14d) was only 5.5%, which showed its good storage property. The microencapsulated formulation killed 70% of test larvae after 7 days in the solar light by the plant leaf test, but the wettable powder with the same dose killed 8.8% of test larvae only, which nearly lose the all activity. The mortality to Heliothis armigera of the microencapsulated formulation decreased from 98.7% to 88.6% after simulated rain (50mm), but dropped from 94.7 % to 37.3% that of the wettabe powder, which showed better adherent property than that of wettable powder.