Understanding Microbial Strain Degradation and How to Prevent It

News 13 11 月, 2024

Microbial strains are critical for various applications, from food safety to pharmaceuticals. However, over time, strains can experience genetic mutations, leading to what is known as microbial strain degradation. This process impacts the viability and productivity of microorganisms and can affect research and production outcomes. Here’s a look at the causes and practical steps for preventing strain degradation.

Causes of Microbial Strain Degradation

Microbial strain degradation occurs due to various genetic mutations, especially during subculturing or in unsuitable storage conditions. Key reasons include:

1. Genetic Mutations: Over many generations, microorganisms can develop mutations that reduce productivity, especially in genes related to production or growth.
2. Delayed Phenotypes: High-yield strains selected for specific traits can sometimes show an initial improvement but decline in performance over repeated testing, often due to delayed expression.
3. Plasmid Loss: In some strains, key metabolic or antibiotic synthesis is plasmid-dependent. Environmental stresses, like high temperatures, can cause these plasmids to detach, leading to strain degradation.
4. Continuous Transfers: Each transfer raises the chance of negative mutations, and with frequent passaging, degraded cells may dominate the population.
5. Poor Cultivation and Storage: Conditions like improper temperature, humidity, and pH can degrade strain viability. These conditions encourage degraded cells to grow and eventually overtake healthier cells.

Preventing Microbial Strain Degradation

Reducing strain degradation requires careful management of culture handling and storage methods. Here are some best practices:

1. Limit Transfers: Avoid unnecessary subculturing and keep transfers to a minimum to lower mutation chances. For certain quality applications, limit passage numbers. Guidelines like those in the Chinese Pharmacopoeia suggest no more than five transfers.
2. Use Ideal Cultivation Techniques: Different cell types respond differently to transfers. For example, using spores instead of mycelium for molds can reduce degradation risks.
3. Optimize Conditions: Use the correct media and maintain ideal environmental settings like temperature, pH, and humidity.
4. Implement Reliable Preservation: Different methods work best for various strains:
   • Transfer Cultivation: Store the revived first-generation strain at 4°C, and transfer it periodically depending on the microorganism type.
   • Glycerol Freezing: Suspend fresh strains in saline and glycerol and store them at -20°C. This method can preserve strains for 1-2 years.
   • Porcelain Bead Storage: For longer storage, strains are absorbed on sterile beads and stored at -70°C for up to 5 years or -20°C for 2-3 years.

Conclusion

Properly preserving microbial strains helps ensure stability and viability. By controlling transfers, optimizing cultivation conditions, and choosing the right storage methods, laboratories can effectively prevent degradation and maintain reliable microbial strains for consistent performance.