[Experience with studying suspension media in actinomycete lyophilization]

Area of Science:

• Microbiology
• Biotechnology
• Pharmaceutical Sciences

Background:

• Long-term preservation of antibiotic-producing microorganisms is crucial for maintaining their viability and productivity.
• Lyophilization (freeze-drying) is a common method for microbial preservation, but the choice of cryoprotectant can significantly impact post-storage characteristics.

Purpose of the Study:

• To evaluate the effects of different cryoprotectants (sodium glutamate, polyvinylpyrrolidone, horse serum) on the viability, cultural characteristics, and antibiotic production of key antibiotic-producing bacteria after 2-year lyophilized storage.
• To determine the optimal cryoprotective agent for preserving the efficacy of antibiotic-producing microbial strains.

Main Methods:

• Antibiotic-producing bacterial strains (producing tetracycline, chlortetracycline, erythromycin, neomycin, oxytetracycline, and polymyxin) were lyophilized in ampoules at 4-10°C using sodium glutamate, polyvinylpyrrolidone, their combination, or horse serum.
• Cultures were stored for 2 years.
• Post-storage assessment included growth rate, cultural features (mycelium color, pigment secretion), and antibiotic production levels compared to controls.

Main Results:

• The highest growth rates were observed in most cultures lyophilized using sodium glutamate.
• Cultures lyophilized in polyvinylpyrrolidone alone exhibited scanty to moderate growth.
• Antibiotic production levels in some strains lyophilized in sodium glutamate or its combination with polyvinylpyrrolidone were slightly higher than controls after 2 years.
• Cultural features remained largely unchanged between lyophilized and agar-maintained cultures.

Conclusions:

• Sodium glutamate is a highly effective cryoprotectant for maintaining the viability and growth rate of antibiotic-producing bacteria during long-term lyophilized storage.
• Preservation using sodium glutamate or its combination with polyvinylpyrrolidone can maintain or even enhance antibiotic production capabilities of certain strains after 2 years.
• Lyophilization using appropriate cryoprotectants like sodium glutamate is a viable method for preserving essential microbial resources for antibiotic production.