Optimization and Characterization of Poly-γ-Glutamic Acid Production From a Locally Isolated Bacillus cereus ARM24

Area of Science:

• Microbiology and Biotechnology
• Polymer Science

Background:

• Poly-γ-glutamic acid (γ-PGA) is a biodegradable polymer with diverse applications.
• Local bacterial sources are valuable for discovering novel γ-PGA producers.
• Efficient production and purification methods are crucial for γ-PGA utilization.

Purpose of the Study:

• To identify and characterize a local bacterium producing poly-γ-glutamic acid (γ-PGA).
• To optimize the fermentation conditions for enhanced γ-PGA production.
• To partially purify and characterize the produced γ-PGA.

Main Methods:

• Screening of 60 Bacillus isolates from various environmental sources.
• Identification of the best γ-PGA producing strain (B3, designated ARM24) using morphological, biochemical, and genotypic analyses.
• Optimization of fermentation parameters (temperature, pH, inoculum size, shaking speed, time) and media components (carbon and nitrogen sources).
• γ-PGA precipitation, purification via dialysis, and characterization using FT-IR, TLC, 1H-NMR, and HPLC.

Main Results:

• Identified Bacillus cereus ARM24 as a potent local producer of γ-PGA, yielding 2.54 g/mL.
• Determined optimal production conditions: 37°C, pH 7, 2 mL inoculum, 200 rpm shaking, 48h fermentation.
• Utilized grape pomace juice and soybean meal with salting out for efficient γ-PGA synthesis.
• Achieved a 3:1 recovery rate of γ-PGA precipitated with 99% ethanol and purified using 10,000 Da dialysis bags.

Conclusions:

• Bacillus cereus ARM24 is a promising candidate for industrial poly-γ-glutamic acid (γ-PGA) production.
• Optimized fermentation conditions significantly enhance γ-PGA yield.
• The characterized γ-PGA demonstrates potential for various biotechnological applications.