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Control of mosquito larvae by encapsulated pathogen Bacillus thuringiensis var. israelensis
1Ankara University, Science Faculty, Chemistry Department, Tandoğan, Turkey.
Abstract:
Bacillus thuringiensis var. israelensis (B.t.i.) containing alginate microcapsules were prepared in order to maintain durable formulations which could resist several effects causing reduced efficiency during applications. B.t.i. spores were harvested through NYSM agar plates and encapsulated in Ca-alginate (0.5-2.0% w/v) gels without any significant loss of sporal or larvicidal activity. The effect of acidic pH on the larvicidal toxin was tested using Culex sp. larvae in the laboratory. The alginate microcapsules pretreated with saturated KH2PO4 solution gave larvicidal activity after 24-48 h, by bioassay. Suspension and encapsulated forms of the pathogenic bacterium were exposed to pH variations (3.0-10.0), UV light and high temperature (50 degrees C). Durability to Pb++, Cu++, Fe++ compounds and phenol was also examined. As the alginate content increased, stability of B.t.i. drastically increased against the tested effects, but to obtain useful releasing microcapsules, 1.0-1.5% w/v alginate concentrations were found to be optimum.
Insights
Bacillus thuringiensis var. israelensis (B.t.i.) alginate microcapsules enhance formulation durability against environmental stressors. Optimized alginate concentrations (1.0-1.5%) maintain larvicidal activity for effective pest control applications.
Area of Science:
- Microbiology
- Biotechnology
- Environmental Science
Background:
- Bacillus thuringiensis var. israelensis (B.t.i.) is a potent biopesticide, but its efficacy can be reduced by environmental factors.
- Developing durable formulations is crucial for maintaining the activity and effectiveness of B.t.i. during application.
Purpose of the Study:
- To develop and evaluate alginate microcapsules for enhanced stability and controlled release of B.t.i.
- To assess the impact of various environmental conditions on the larvicidal activity of encapsulated B.t.i.
Main Methods:
- B.t.i. spores were encapsulated in calcium alginate gels at varying concentrations (0.5-2.0% w/v).
- Encapsulated and suspension forms of B.t.i. were subjected to pH variations, UV light, high temperature (50°C), and chemical stressors (Pb++, Cu++, Fe++, phenol).
- Larvicidal activity was determined through bioassays using Culex sp. larvae.
Main Results:
- Alginate microencapsulation preserved the sporal and larvicidal activity of B.t.i.
- Increased alginate concentration significantly enhanced the stability of B.t.i. against tested stressors.
- Optimum alginate concentrations of 1.0-1.5% w/v were identified for balancing stability and useful release characteristics.
Conclusions:
- Alginate microcapsules offer a promising strategy for creating stable and effective B.t.i. formulations.
- Optimized alginate concentrations are key to achieving durable B.t.i. formulations with sustained larvicidal activity.
- This approach can improve the reliability and efficiency of B.t.i. in pest control applications.