Subculture and Preservation Methods
Some microorganisms are sensitive to environmental changes such as freezing or drying, which can cause them to die quickly. In such cases, subculture preservation is often the most practical method. Subculture involves regularly transferring microbial strains to fresh media and preserving them after cultivation. This is one of the most fundamental techniques used in microbial preservation, commonly applied to everyday strains like those used in yogurt production.
When performing subculturing, it's important to use a medium with moderate concentration and balanced nutrients. The carbohydrate content should be kept low to avoid overgrowth. The incubation temperature is usually slightly lower than the optimal growth temperature for the organism. For acid-producing strains, a small amount of calcium carbonate can be added to the medium to neutralize excess acidity.
Most microorganisms are best preserved at 5°C. However, certain types, such as anaerobic bacteria, *Vibrio cholerae*, and some pathogenic fungi, may require storage at 37°C. Large edible fungi, like mushrooms, can often be stored at room temperature without issue.
While subculture preservation is simple and cost-effective, it has several drawbacks:
1. The cotton plug in culture tubes is prone to mold contamination.
2. Strains may undergo genetic mutations over time.
3. The pathogenicity, physiological activity, and spore-forming ability of the strain may decrease.
4. Regular transfers are required, which increases labor and workload.
5. There is a higher risk of contamination during each transfer.
In addition to subculture, there are various other preservation methods available, such as cryopreservation, lyophilization, and storage in mineral oil. Each method has its own advantages and limitations depending on the type of microorganism and its stability.
Due to character limits, this summary provides an overview of subculture preservation. For more detailed information on different preservation techniques, you're welcome to download our full article. Simply click the download button to get the file for free. Don't forget to unzip the file after downloading! Shanghai Hengyuan looks forward to serving you!
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