How to Culture a Probiotic

How to culture a probiotic

This blog post will be part of a mini-series on probiotics, be sure to check out Matt's other resources and to sign up to stay up to date with his new releases.

This blog post is NOT A RECIPE but rather, a deep dive into truly understanding a microbe so that when we go to develop a recipe, it has a higher success rate.

What does a microbe need to survive?

Microbes require certain conditions to effectively multiply and grow. If we would like to culture these microbes from a probiotic or food source we need to give them a space where they can grow in but also a space where other microbes cannot grow in. These are the main factors we need to consider:

1. Temperature Range - What temperature does this microbe prefer. Too cold and it'll go into hibernation (it wont die, but it wont multiply) and too hot and it will die. The correct temperature range needs to be applied for success

2. Oxygen availability - Does the microbe need oxygen or not? Does it maybe do better in an oxygen poor environment?

3. Food Source - What sugars are these microbes eating to multiply? You cannot just give a microbe any type of sugar and hope it will grow in a yogurt culture. You need to respect the microbes preferences if you want it to grow!

All of these factors can be determined with an online database. BacDive (pictured below) is a bacterial database that can be used to determine what will work best.

This website will help us determine how to culture a probiotic in a home kitchen

Simply type in your microbe of interest and look up it's preferred conditions.

L. Reuteri will be used in today's example

L. Reuteri culturing

Link to webpage used

1. Temperature range: L. Reuteri grows in 30-45°C (86-113°F) and seems to prefer 37°C (98.6°F) which is technically body temp. In other words, this microbe will easily grow in the warm 37°C gut.

2. Oxygen tolerance: L. reuteri prefers little to no oxygen. This means that fermentation should be done in a closed environment. Semi-sealed also works (for example, in a jar with a screw-top lid that has a 1/4 turn undone)

3. Preferred food source: L. Reuteri only eats specific sugars or specific metabolites (outlined below) it will not ever eat other sugars.

L. Reuteri preferred metabolites:

• Galactose

• Glucose

• Ribose

• Arabinose

• Lactose

• Maltose

• Melibiose

• Raffinose

• Sucrose

From all of these metabolites L. Reuteri will ferment.

L. Reuteri will NOT eat:

• Fructose and fucose

• Inulin (chain of fructose molecules)

• Any starch

Source link - Scroll down to Metabolite utilization and click to see all entries. '+' means that it does eat that sugar/metabolite '-' means that it does not eat that sugar/metabolite.

How to ferment L. Reuteri

1. Pick how you want to feed it : A milk medium or a plant-based medium with sugar/honey added to it

2. Sterilize the medium by heating it up then cooling it down

3. Measure pH - it should be neutral this is your starting marker to see if the bacteria has fermented after incubation

4. Inoculate the medium with the L. Reuteri and any additional sugars

5. Close the environment by sealing the jar

6. Put it into an incubation chamber (oven, yogurt-maker, sous vide, etc.) to ferment at 37°C

7. Let the bacteria eat the sugars provided. They will make acid as a result.

8. Check fermentation progress from time to time. You will be able to see a gelled yogurt-like protein matrix when it is done.

9. Once you see that it has set, check the pH once again. If the pH has dropped and it is now acidic that means you have been successful with your fermentation.

10. Store in the refrigerator and consume within 2 weeks. Set aside a portion for a future batch.

Notes:

• The thickness of your yogurt is NOT an indicator of success, watery or loose yogurt is only an indicator of how much water content you have in relation to the amount of solids you have in your end product. If you want a thicker end product, add more solids. For example, add milk powder (more lactose sugars) to your milk or add more sugar to your plant-based milk (like honey).

Thank you for reading!
-Matt

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Purchase Matt's L. Reuteri Yogurt Recipe Matt available on Etsy.
(Video tutorial coming soon)