Preservation Methods for Pure Cultures

• Preserving pure cultures is essential for maintaining bacterial viability and genetic stability over extended periods.
• Common preservation methods include:

Refrigeration of Preservation Methods for Pure Cultures

• Temperature: 4°C
• Duration: Short-term storage (weeks to months).
• Procedure: Cultures are stored on agar slants or in broth media in a refrigerator.
• Advantages: Simple and easy for short-term use.

Freezing of Preservation Methods for Pure Cultures

• Temperature: -20°C to -80°C
• Duration: Long-term storage (years).
• Procedure: Cultures are mixed with a cryoprotectant (e.g., glycerol) to prevent ice crystal formation and stored in a deep freezer.
• Advantages: Effective for long-term preservation with high viability.

Lyophilization (Freeze-Drying)

• Procedure: Cultures are frozen and then subjected to a vacuum to remove water by sublimation, leaving a dry powder.
• Storage: The powder is sealed in ampoules or vials and stored at room temperature or in a refrigerator.
• Advantages: Very long-term storage (decades) maintains viability and genetic stability.

Cryopreservation in Liquid Nitrogen

• Temperature: -196°C
• Duration: Very long-term storage (decades).
• Procedure: Cultures are suspended in a cryoprotectant and stored in liquid nitrogen.
• Advantages: Maintains high viability and genetic stability over very long periods.

Use of Culture Media Additives

• Procedure: Addition of substances like glycerol, dimethyl sulfoxide (DMSO), or skim milk as protectants during freezing.
• Goal: Enhance survival rates during storage and thawing.
• Advantages: Increases the effectiveness of freezing methods.

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