PREPARATION AND BIOASSAY OF BACILLUS THURINGIENSIS MICROCAPSULES BY COMPLEX COACERVATION

In this study, the gelatin-gum arabic microcapsules loaded Bacillus thuringiensis (Bt) were prepared by complex coacervation. Based on single factor experiment and orthogonal test, the preparation process parameters such as encapsulating temperature and pH, the concentration of getatin and gum Arabic, and rotational speed were investigated and optimized The obtained optimum parameters of preparation were as follows: the encapsulating temperature and pH were 40 degrees C and 3.9, the concentration of getatin and gum arabic were 10 g(-1)L(-1), the volume ratio of core (10(10)cfu/L Bt suspension) to wall (10 g(-1)L(-1) gelatin and Arabia gum solution ) was 1:2, and stirring speed was 350 rpm. With the optimized preparation process, the size and span value of obtained Bt microcapsule were about 12.7 mu m and 1.03, and encapsulation efficiency was up to 87%. The experiment of biological activity to grub showed that the Bt microcapsule had better persistent effect compared with the control, when the number of spores was 109cfu(-1)ml(-1), the mortality of grub were 75.65% and 86.09% on the 7th and the 14th day.