Microplate-based quantification of poly-γ-glutamic acid levels in biofilm samples.

Area of Science:

• Microbiology
• Biochemistry
• Biotechnology

Background:

• Poly-γ-glutamic acid (PGA) is a valuable biopolymer with diverse applications in medicine and industry.
• Optimizing PGA production and yield is crucial, requiring efficient methods for strain identification and condition determination.
• Existing screening methods for PGA production may lack the sensitivity or reproducibility needed for biofilm research.

Purpose of the Study:

• To develop and validate a sensitive and reproducible assay for quantifying poly-γ-glutamic acid (PGA) in Bacillus subtilis biofilms.
• To establish a reliable method for comparative analysis of PGA production across different strains, treatments, and environmental conditions.
• To facilitate research aimed at enhancing PGA yields and recovery.

Main Methods:

• A novel assay utilizing the spectral shift of methylene blue upon binding to PGA was developed.
• Protein-free PGA standards were prepared from lyophilized Bacillus subtilis NCIB 3610 ΔtasA liquid cultures grown at 50°C.
• Quantification was achieved using standard curves based on methylene blue absorbance at 564 and 664 nm in a 96-well plate format.

Main Results:

• The assay demonstrated sensitivity and reproducibility in quantifying PGA from Bacillus subtilis biofilm extracts.
• The quantification protocol was validated, and interference-minimizing treatment steps were identified.
• The 96-well plate format allows for high-throughput analysis with minimal sample volume and reduced consumable waste.

Conclusions:

• The developed methylene blue-based assay provides a sensitive and reproducible method for PGA quantification in biofilm research.
• This assay facilitates comparative studies, essential for optimizing PGA production and identifying high-yield strains.
• The method's efficiency and low sample requirement support broader research into biopolymer applications and production enhancement.