Microbe Mondays: Kombucha

Microbe Mondays: Kombucha

What is Kombucha?

Kombucha is sweetened black or green tea that is fermented with a symbiotic colony of bacteria and yeast (SCOBY). It is thought to have originated in China and spread east through Russia, Germany, and Western Europe. Though kombucha is made with sugar, most of it is broken down through the fermentation process.

Kombucha cultures can vary in bacterial and yeast composition. The most common strains of bacteria are Gluconacetobacter xylinus, Bacterium gluconicum, A. aceti, and A. pasteurianus. The most common yeast strains are Saccharomyces cerevisiae, Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbruekii, Saccharomycodes ludwigii, and Zygosaccharomyces bailii. As a general rule, the yeast produces alcohol, which can help bacteria to produce acetic acid. Because of this conversion process, the alcohol content of kombucha remains quite low and the drink increases in acidity the longer it ferments.

Why Drink Kombucha?

The bacteria and yeast present in kombucha have numerous beneficial effects as far as preservation of the beverage itself and potential health effects for those who drink it. To start with, kombucha is a very safe ferment to make at home. Because of the acidity, ethanol content, and catechins, kombucha is largely resistant to contamination by harmful organisms.

Some of the benefits of kombucha can be attributed to the known health effects of tea (discussed in a previous post), but there are other benefits that are unique to the drink. The bacteria and yeast in kombucha produce numerous healthful compounds, including amino acids, enzymes, polyphenols, and some micronutrients. Kombucha is?a natural probiotic and the bacteria themselves assist with digestion and nutrient absorption.

There is evidence that the fermentation process promotes B vitamin synthesis. Various studies also suggest improved immune and liver function and lowered cancer risk associated with long-term consumption of kombucha. It may also be effective against pathogenic bacteria such as H. pylori, E. coli, S. aureus, and A. tumefaciens. The antimicrobial activity is likely due to the acetic acid content.

And on top of all the potential health benefits, it tastes really good!

Making Kombucha

There are a lot of different kombucha brands out there, but I always prefer to make my own. It?s much less expensive, generally lower in sugar, more sustainable (shipping glass bottles around the country uses a lot of fuel), and likely has a higher probiotic content than kombucha from the store.

Kombucha is my favorite ferment to make because it?s simple to make and hard to mess up.


Water (preferably filtered and free of chlorine)
Black or Green Tea
Starter tea (previously brewed kombucha) or vinegar (distilled or apple cider)
Large glass container to store the kombucha


  • Boil water
  • Pour over tea and steep for at least 10 minutes
  • Add sugar and stir until dissolved
  • Wait until the tea cools to room temperature
  • Add the scoby and starter tea or vinegar
  • Cover with a clean dish towel, coffee filter, or a paper towel that has been folded over a few times, and ?seal? with a rubber band
  • Store in a dark place such as a pantry for at least 1 week (I ferment mine for 3-4 weeks, then pour it into bottles and use the remains of that batch to start a new one)

I make half gallon batches and use the following measurements:

  • 7 cups water
  • 1 tablespoon loose leaf tea (could also use 3-5 tea bags)
  • 1 cup sugar
  • 1 cup starter kombucha from my previous batch (same amount if using vinegar)

This table from Cultures for Health gives?recommendations for making different volumes of kombucha.

Container SizeTeaSugarWaterStarter Tea or Vinegar?
One quart1-1/2 teaspoon loose tea or? 2 tea bags1/4 cup2 to 3 cups1/2 cup
Half-gallon1 tablespoon loose tea or ?4?tea bags1/2 cup6 to 7 cups1 cup
Gallon2 tablespoons loose tea or 8?tea bags1 cup13 to 14 cups2 cups


Dufresne & Farnworth. (2000). Tea, kombucha, and health: A review. Food Research International, 33, 409-421.

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