Chitosan-based Pickering double emulsion microcapsules improve the UV stability and the persistence of Bacillus thuringiensis on mosquito control.

Bacillus thuringiensis (Bt) is affected by ultraviolet radiation and bacterial sedimentation in pest control applications, leading to low pesticide utilization and a short duration of control. To improve Bt stability in these applications and prolong the duration of biological control, Bt LLP29 was first encapsulated using double emulsion technology, resulting in the formation of W/O/W double emulsion microcapsules with sodium lignosulfonate and chitosan as wall materials. The morphological structure and functionality of microcapsules were then systematically investigated. Notably, the survival rates of Bt bacteria and spores in the microcapsules were maintained at 22.98 % and 8.18 % after 96 h of UV irradiation, and the retention rate of insecticidal protein was increased by 41.42 % after 72 h, with high mosquito-killing activity maintained. Furthermore, the Bt microcapsules exhibited excellent suspension properties and sustained release capabilities, which enhanced the retention of Bt active ingredients in the environment of young mosquitoes and extended the duration of pest control. These studies pioneered the application of double emulsion technology and microcapsules to the encapsulation of Bt based on the functional properties of chitosan. This will pave the way for the development of multifunctional Bt preparations in agricultural applications and pest control.