Preservation Techniques (Lyophilization, Subculturing)

Back to: MICROBIOLOGY 400 LEVEL

Welcome to class!

Hello, brilliant scholar! It’s great to have you here again. You’ve been doing so well, and I can see you growing more confident with each lesson. Today, we’re going to talk about a very practical and essential topic in microbiology—Preservation Techniques. Just like how we preserve our ogbono, pepper, or yam to use later, scientists also need to preserve microorganisms so they don’t lose them over time. Let’s make this simple and very relatable.

Preservation Techniques (Lyophilization, Subculturing)

Microbes used in the lab or industry can lose their strength, die, or mutate if not preserved properly. Imagine if a bakery had to find new yeast every single day—it would be stressful and wasteful! Preservation techniques help scientists keep valuable microbes alive and unchanged for long periods without needing to grow them daily.

Let’s now look at two common techniques: lyophilization and subculturing.

Lyophilization (Freeze-Drying)

Lyophilization is a fancy name for a process that removes water from a microbial culture by freezing it and then drying it under a vacuum.

Here’s how it works:

The microbe is first grown in a suitable medium.

The culture is frozen.

Then, using a machine, water is removed as vapour (not liquid) under low pressure.

The dried microbe is sealed in a container and stored at cool temperatures.

This technique is great because:

Microbes can survive for years.

It reduces the risk of contamination.

It’s easy to transport and store.

Imagine it like how we dry crayfish or dry locust beans in the sun—they last longer and can be used later. Lyophilization does the same for microbes, but in a more controlled lab setting.

Subculturing

Subculturing means transferring microbes from an old medium to a fresh one at regular intervals to keep them alive and active.

Steps:

A small portion of the microbial culture is taken.

It is transferred to fresh nutrient medium under sterile conditions.

The new culture is incubated and grown again.

It’s simple and commonly used in many labs, but it has some downsides:

The microbe can change over time (mutation).

It requires more hands-on work.

There’s a higher risk of contamination if not done carefully.

Think of subculturing like how we keep some of our old yam for planting new ones each season. It’s effective, but you have to monitor and replant carefully each time.

Summary

1. Preservation techniques keep microbes alive and useful over time.
2. Lyophilization (freeze-drying) removes water and keeps microbes stable for long-term storage.
3. Subculturing involves regularly transferring microbes to fresh media to maintain them.
4. Lyophilization is safer for long-term storage, while subculturing is simple and good for short-term maintenance.
5. Both methods help scientists and industries save time, cost, and valuable microbial strains.

Evaluation

• Why is it important to preserve microorganisms?
• What is lyophilization, and why is it useful?
• State one advantage and one disadvantage of subculturing.

You’re not just learning microbiology—you’re building skills that solve real-world problems. Keep believing in yourself. Afrilearn is always here to guide and support your learning journey. See you in the next exciting class!