Abstract：Bacillusthuringiensis (Bt) is a gram-positive and spore-forming bacteria. It can form parasporal crystal during spore-forming, which is specific toxic to many insects. Bt formulation is a microbial bioinsecticide, which is the largest produced and the most widely used. But the Bt formulation is sensitive to UV in the application process, thus shortens the duration of active ingredient, which the disadvantage would limit the application of Bt formulation. Improving the biological insecticidal activity and UV-resistant ability of Bt insecticidal crystal protein by loading with nanomaterialsis is regarded as a promising technology, due to its advantages of small particle size, large specific surface area, high efficiency and low toxicity, environmental-friendly properties and improving the stability of Bt preparations. In the present study, Bt insecticidal crystal protein was loaded with nano-Mg(OH)2 to understand the compound biological insecticidal activity and resistance to UV. The nano-Mg(OH)2 was prepared by co-precipitation of magnesium chloride hexahydrate and sodium hydroxide, and the X-ray powder diffraction (XRD) was applied to analyze the size of synthesized nano-Mg(OH)2, and the size of nano-Mg(OH)2 at (101) direction was 12 nm according to the scherrer equation. Scanning electron microscope (SEM) analysis showed that the sample contained a lot of small nano-flakes structure with uniform dispersion, and the morphology of Mg(OH)2 particles loading with Cry toxin had no obvious changes. Bt LLP29 was selected as a target strain because it had high insecticidal activity to mosquitoes (Culicidae), and the Bt insecticidal crystal protein was obtained by alkali soluble method. Results of sodium dodecyl sulfonate - polyacrylamide gelelectrophoresis (SDS-PAGE) and bioassay indicated that the loaded nano-Mg(OH)2 could effectively improve the insecticidal activity of protein, protect the protein structure from destructing, and enhance the ability of resistance to ultraviolet radiation. The present work provides the fundamental information to gain biocompatibility and environmental-friendly nano-formulation of Bt bioinsecticide.
