Evaluation of the strategy for insecticidal crystal encapsulation with cell wall in industrial processes.

Background: Bacillus thuringiensis (Bt) can produce insecticidal crystal proteins during sporulation, and these are the basis of the most successful microbial insecticides in use today. However, the susceptibility of insecticidal crystal proteins to inactivation by ultraviolet (UV) radiation from sunlight causes damage to the insecticidal crystals and subsequent loss of toxicity. The deletion of the mclX gene, an unknown functional gene, can make the insecticidal crystal proteins become encapsulated by the cell wall which provides some protection against UV radiation. This study evaluates the potential of this innovative strategy during the industrial process of commercial strain KN11.

Results: Gene mclX was deleted from a commercial Bt strain KN11 successfully, and the mutant strain was cultured under different conditions, including laboratory and industrial fermentation conditions. The mother cells of the mclX mutant strain remained nonlysed after industrial processes. The deletion of mclX had no adverse effects on the production of Cry1Ac protein and no impact on the insecticidal activity. Most noteworthy, the ΔmclX mutant had improved UV resistance and insecticidal activity compared to the wild-type KN11 strain.

Conclusion: This finding suggests that commercial strains can be genetically modified to encapsulate insecticidal crystal in Bt products using the mclX mutation strategy. This study evaluated the ability of commercial strains lacking the mclX gene to encapsulate crystals giving resistance to UV radiation. © 2024 Society of Chemical Industry.