culturing kombucha microbes – Part 1

Kombucha relies on a symbiotic relationship between various yeasts and bacteria known as a SCOBY (symbiotic culture of bacteria and yeast). These microorganisms are passed down from the mother SCOBY to each new baby SCOBY. The physical structure of the SCOBY is made primarily of cellulose and it helps to protect the culture from invaders.

Most kombucha brewers maintain their cultures by continually passaging their SCOBYs from one batch of fresh sweet tea to the next or by housing them in a SCOBY Hotel. However, advanced brewers may want to isolate the various strains of bacteria and yeast and work with them directly. Benefits of working with these microbes individually include greater control over the fermentation process, the ability to make custom culture blends with unique characteristics, and indefinite preservation.

While this might seem daunting, this article describes all of the materials and techniques necessary to isolate and work with kombucha microbes in a home environment.

Step One - making Petri plates at home

  • Difficulty: moderate
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Growing kombucha microbes on a solid surface, rather than in the liquid sweet tea, allows them to be isolated from each other. Petri plates are a common way to do this. Pre-poured Petri plates are available from online retailers, but preparing Petri plates at home, as described below, is easier than most people think. Give it a try before spending more for pre-poured plates.

Materials and Equipment

Directions

  1. Remove 6 empty petri plates and set aside.
  2. Cut a small 6″ x 6″ square of parchment paper or aluminum foil. Make a single diagonal fold from one corner to the opposite corner (making a triangle). Unfold the square and place on the kitchen scale such that the powder you will add in the next step will fall into the crevice formed by the fold. Tare/zero the scale.
  3. Carefully measure out 6.5g of Sabouraud Agar by using a small spoon to transfer powder to the crevice in the folded parchment paper or aluminum foil.
  4. Transfer the 6.5g of Sabouraud Agar to the Pyrex flask or large measuring cup. (Measuring cup should be at least 500 ml in volume). Add 100 ml filtered water. Swirl to suspend the powder. Note: It will not dissolve at this stage.
  5. Transfer to a microwave. Microwave in increments of 15 seconds. Between each heating step, swirl using an oven mitt to protect from the heat. Observe the liquid between each heating increment. When all of the agar is thoroughly dissolved and the liquid is clear, proceed to Step 6. WARNING: Do not microwave for longer than 15 seconds at a time. Watch the microwave and stop it immediately if you see the liquid start to boil over.
  6. Allow the liquid to cool for 10-15 minutes. (It is okay to leave it in the microwave for this stage, so that airborne microbes do not contaminate the agar).
  7. Using silicone oven mitts with a very good grip, carefully remove the flask or measuring cup from the microwave.
  8. Remove the lid from the first Petri dish and carefully pour enough liquid agar to just barely cover the bottom of the dish. Replace the lid and repeat with remaining Petri dishes. This recipe should provide enough agar for 5 or 6 dishes.
  9. Allow Petri dishes to cool to room temperature on a flat surface. At this point, the agar should be solid. Invert Petri dishes (agar side up) for storage.

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