Endospore dipicolinic acid detection during Bacillus thuringiensis culture

Area of Science:

• Microbiology
• Biotechnology
• Bioprocess Engineering

Background:

• Bacillus thuringiensis endospore production is critical for bioinsecticide efficacy.
• Detecting endospore formation in complex industrial media is challenging due to high solid content.
• Accurate monitoring of sporulation is essential for optimizing fermentation processes.

Purpose of the Study:

• To develop and validate a method for detecting Bacillus thuringiensis endospore production.
• To overcome challenges in endospore detection within complex industrial fermentation media.
• To establish a reliable indicator for the onset of sporulation in industrial settings.

Main Methods:

• Utilized the photoluminescence of dipicolinate (DPA) complexed with Tb3+ to quantify endospores.
• Employed high temperature and pressure (autoclaving) to efficiently release DPA from endospores.
• Conducted fermentations using Bacillus thuringiensis var. kurstaki HD-73 in industrial-type media with varying nutrient concentrations.

Main Results:

• Successfully determined dipicolinate (DPA) concentrations during Bacillus thuringiensis fermentation in high-concentration soybean meal media.
• Established a strong correlation between traditional microscope endospore counting and DPA-based measurements.
• Demonstrated the feasibility of detecting endospore production under industrially relevant, challenging conditions.

Conclusions:

• The DPA photoluminescence method provides a reliable way to quantify Bacillus thuringiensis endospores in complex media.
• This method enables accurate determination of sporulation initiation, vital for bioinsecticide production.
• The findings support improved process control and optimization in Bacillus thuringiensis industrial fermentations.