Bacillus Thuringiensis (bt) The Development Of Micro-capsules

Due to Bacillus thuringiensis biologic activity and their poor power in preventing from ultraviolet, Bacillus thuringiensis is prone to lost activity and to represent instability because of bad condition during the course of prevention and cure in the field. So, it is important to select appropriate preparation to assure the stability in deposited and to exert the full measure of its effect in the field. Microcapsule preparation was known as one of the best controlled release preparation, It was shown that the resistance to harmful conditions is strengthened, it would last the effect when it used in the field and could enhance its storing stability. Microcapsulation of the excellent strain of Bacillus thuringiensis that selected from 4 strains of Bacillus thuringiensis in used widely was studied in this paper. The conclusions have been obtained as follows:1. Selecting and culturing Bacillus thuringiensis stain. The appearance, characteristic and resistance to harmful conditions related to microcapsulation was studied on the present four stains of Bacillus thuringiensis, The excellent Bacillus thuringiensis strain(Btl) is separated from bacterium preparation of yangzhou. The resistant to ultraviolet irradiation is poor and its activity come down from 100% to 60% after irradiating 2 hours.2. Microcapsulation process. The microcapsulation methods of Bacillus thuringiensis, such as phase separation-coacervation, double phase separation-coacervation and freeze immersion were studied in this paper, the microcapsules preparation which made by the double phase separation-coacervation method was better than the other preparation in terms of their inwrap rate, average diameter, storing stability. The microcapsulation materials of double phase separation-coacervation, such as Gelatin glue-Acacia glue, Gelatin glue-Pectin glue, Gelatin glue-Alginic glue, Gelatin glue-Sodium Carboxymethyl Cellulose glue were also studied. The above-mentioned parameter of two former materials were better than other materials evidently.3. Tested poisonous power of microcapsules. The small cabbage moths were fed treated vegetables that immersed 3min microcapsules suspension and dried by airing, then lighted up by ultraviolet 2 hours. The poisonous power to small cabbage moths treated by the Gelatin glue -Acacia glue microcapsule and Gelatin glue-Pectin glue microcapsule were higher. Accordingly, their rectified death rate to small cabbage moth was 66.7% and 60% separately. The similar results gained in silkworm's testing of poisonous power and the rectified death rate of the Gelatinglue -Acacia glue microcapsule and Gelatin glue-Pectin glue microcapsule to silkworm's rectified was 60% and 50% separately.In terms of inwrap rate, average diameter, storing stability, virulence test of microcapsules preparation, confirmed that the double phase separation-coacervation method with the Gelatin glue-Acacia glue or the Gelatin glue-Pectin glue was the better the preparation method.The best technique conditions of the microcapsules preparation with the Gelatin glue-Acacia glue were: the concentration of Bacillus 1%, the concentration of Gelatin glue and Acacia glue 3% separately, the system temperature 50 and the rotate speed 200r/min. Its inwrap rate was 80.1%, and average diameter was 53.6 n m.The best technique conditions of the microcapsules preparation with the Gelatin glue-Pectin glue were: the concentration of Bacillus 5%, the concentration of Gelatin glue 5, Pectin glue 3%, the system temperature 40 and the rotate speed 300r/min. Its inwrap rate was 83.2%, and average diameter was 55.5 u m.