When we’re making kombucha, we want it to be as healthy and as health-giving as we can. Because even though it tastes great, most of us are doing this because of kombucha’s health benefits.

We want to see improvements in our health. Otherwise, why bother, right?

So, let’s dive into the exciting world of lactic-acid bacteria, and how they benefit your kombucha brew.

You might remember this other research paper about kombucha probiotics being different in every scoby, where we found out that, while most of us assume that our kombucha scoby is doing lacto-fermentation, that this might not be the case. Not all kombucha scobys have got lactic-acid bacteria (also called lactobacilli). And if there are no lactic acid bacteria there is no lacto-fermentation.

Now, this isn’t to say that a scoby without lactobacilli is useless. Not at all. But there are a few good reasons why you might want to encourage some to take up residence in your fermentation vessel.

And that is what this month’s paper is all about.

As an aside, the type of sugar you use can impact on how much lactic acid is produced too. Check out this post on the best sugar for kombucha.

Key take-home points about kombucha probiotics:

Kombucha lactobacillus work well together with acetic acid bacteria (the bacteria that give kombucha its vinegary ‘bite’). They are both more productive and more stable in each other’s company.

When some types of lactobacilli are added, the kombucha

1. Produces more glucuronic acid

2. Has got better antibacterial properties (including against known baddies like Salmonella and Listeria)

3. Is a more effective antioxidant (in the test-tube, anyway)

So YES, you do want Lactic Acid Bacteria in your kombucha.

See this post about kombucha refrigeration for more information about keeping the LAB happy.

The kombucha research paper

“Lactic acid bacteria: promising supplements for enhancing the biological activities of kombucha.”

Find it at Nguyen et al. SpringerPlus (2015) 4:91

This month’s researchers are based in Ho Chi Minh City, Vietnam. They have published several other papers on kombucha. This research group generally appears to focus on industrial microorganisms and fermentation technology.

So before we dive into this paper, let’s back up a little bit and have a quick overview of what the researchers already knew before they started.

What the researchers already knew:

This research group had already done some research in which they took some lactobacillus from kefir and added it to kombucha.

One of the main types of bacteria in kombucha are acetic acid bacteria. They are the ones responsible for its vinegary taste and are commonly found in natural vinegars, too. What the researchers found was that when you mix the acetic acid bacteria from kombucha and the lactic acid bacteria from kefir together, both grew better together than they did separately.

They also knew, from other people’s research, that kombucha has three properties that are generally thought to be health-promoting: 1. Glucuronic acid production, 2. Antibacterial activity, 3. Antioxidant activity.

I’m going to take a short detour here to quickly chat about each of these properties, because they’re quite important if you’re interested in the health effects of kombucha.

Related: Why kombucha is good for you

Glucuronic acid production in kombucha

There has been a bit of controversy about whether or not kombucha actually contains glucuronic acid. Some people claim that it doesn’t, and others that it does. My personal theory is that this is due, at least in part, to the wide variability that exists between scobys of different origin (see my earlier blog post about this). I think it entirely feasible that the scoby held by one laboratory will produce low levels of glucuronic acid, while another will produce higher levels. Until we can track down exactly which microbe, or group of microbes, is making the glucuronic acid, this will remain a bit of a mystery.

But why do we care? Because glucuronic acid is made by your own liver as a detoxifying agent. The key role that glucuronic acid has in the body is binding to chemicals your body doesn’t want and escorting them to the liver and kidneys for processing and elimination.

Key point: Kombucha makes an important de-toxing chemical.

Kombucha’s antibacterial activity

Kombucha is also a bit of a star at killing unwanted microbes. This is at least partly due to the acetic acid content of the kombucha, and is similar to the benefits that are often touted for Apple Cider Vinegar.

However, as we saw with the recent post about kombucha’s anti-viral properties, there may be more to it than kombucha simply being acidic.

Key point: Kombucha kills germs.

Kombucha’s antioxidant activity

Kombucha has a range of antioxidants in it.

Antioxidants are used by the body to counter the effects of free-radicals, and to combat Oxidative Stress.

I talk about this some more in my book Simply Kombucha but, in brief, we encounter lots of free-radicals in our food and environment, and we even produce them in our bodies as a waste-product of many biochemical processes. We also produce antioxidants that go around mopping up these free-radicals before they can do damage. Except that sometimes we don’t produce enough antioxidants, and our bodies can come under what is called Oxidative Stress. Depending on which parts of the body are affected, Oxidative Stress can contribute to heart disease, cancer, and other disease processes.

Eating and drinking antioxidants seems to help, although the exact relationship between a chemical’s antioxidant power in the test-tube, and that chemical’s activity in the body is not clear.

Key point: Kombucha is an antioxidant

What these researchers were trying to find out

So, back to our friends in their lab in Vietnam.

They were trying to find out two things:

Does it matter where the lactic acid bacteria come from? Is it better to take them from kefir or kimchi, for instance, or does it make no difference? Do the health-giving properties of kombucha increase, decrease, or not change, when lactic acid bacteria are added?

What they did

First, they went shopping.

The research paper says that they found pickled cabbage, kefir grains and kombucha scobys in their local market in Ho Chi Minh City. So they purchased those and took them back to the laboratory.

They cultured up the kombucha and kefir, and then isolated lactic acid bacteria from the kefir, pickled cabbage and kombucha.

Then they set up the following cultures:

Plain black tea + sugar Kombucha with nothing else added Kombucha + “Lac1” one type of lactic acid bacteria from pickled cabbage (not identified) Kombucha + “Lac2” a different type of lactic acid bacteria from pickled cabbage (not identified) Kombucha + “Lac3” lactic acid bacteria from kombucha (L. plantarum) Kombucha + “Lac4” one type of lactic acid bacteria from kefir (L. plantarum) Kombucha + “Lac5” a different type of lactic acid bacteria from kefir (L. casei)

Then they measured glucuronic acid production, antibacterial activity and antioxidant activity of each culture.

What they found

Now, here is where it gets interesting. The researchers claim that they got a clear ‘winner’, and that the lactic acid bacteria from the kefir gave them universally better results than the others, but I think the results are less clear than that.

What muddies their results considerably is that the kombucha scoby that they used already had lactic acid bacteria in it (I know this because they used it to isolate their “lactic acid bacteria from kombucha” for culture 5, above). So they are not comparing a scoby with lactic acid bacteria to one without. They are taking a scoby that already has Lactobacillus plantarum in it, and adding different lactic acid bacteria to it to see what happens.

They also didn’t identify which lactic acid bacteria they had isolated from the pickled cabbage, so it’s hard to draw conclusions about this. There are at least 12 different species of lactobacillus (and possible up to 180, depending on how you classify them), so this would have been good information to have.

But in brief, the results were:

Glucuronic acid production

If you’re a visual person, click through to the paper, and look at Figure 1. I can’t paste the image in here without breaching copyright, but it’s a very straight-forward graph.

Unfermented tea showed no glucuronic acid All the kombucha cultures showed significant amounts of glucuronic acid. The “Lac5” culture (culture 7 in my list, above) showed significantly more than the others.

For Glucuronic acid production, adding Lactobacillus casei from kefir was a clear winner.

Anti-microbial activity

In this test it’s a bit trickier to spot a winner. They tested each of the seven cultures against four pathogenic microbes;

The table of results can be seen here

The results are a bit higgeldy-piggeldy, but the “Lac3” culture (culture 5 in my list, above) was better at killing the pathogenic bacteria than the other cultures. So the clear winner here was adding Lactobacillus plantarum from kombucha, to kombucha, which already had some of that same lactobacillus in it.

Which is interesting. I would like to see this experiment repeated, to be honest, to see if they come up with the same results, or if there are some other variables to explain the differences between the cultures.

But regardless, all of the cultures with added lactic acid bacteria performed better than the original kombucha culture when it came to fighting the pathogenic bacteria. But it made no difference whether those lactic acid bacteria came from the cabbage or the kefir.

Antioxidant activity

For the relevant results table click here

They used Vitamin C as their ‘gold standard’ of antioxidant activity and compared the cultures to see how they did.

“Lac4” (culture 6 in my list, above) performed as well as Vitamin C The original kombucha culture, “Lac3” (culture 5) and “Lac5” (culture 7) all performed about the same as each other. They were a step down in activity from Vitamin C, but not too shabby. “Lac1” (culture 3) and “Lac2” (culture 4) were the poorest performers, beating only the unfermented tea.

Adding Lactobacillus plantarum from kefir was the clear winner when it came to antioxidant activity.

What does this mean for us?

Basically, it means that we want to make sure that our kombucha scobys have got lactic acid bacteria in them.

Now, without access to petri dishes and a reliable way to isolate and identify bacteria, we can’t actually tell if our existing scobys have got lactic acid bacteria in them or not, or which types we’ve got if we have. So if you want to be certain, I’d just go ahead and add some, and then you know that you’re sorted.

How to add lactic acid bacteria to your kombucha

Way back in the first research paper I looked at we met another group of researchers, from South Africa, who successfully added lactic acid bacteria to their scoby by adding some chopped cabbage to their brew. They also showed that the lactic acid bacteria stayed as part of the scoby from then on, through multiple generations.

Today’s study suggests that adding a couple of spoons of milk kefir whey to a kombucha brew would achieve the same thing, and may even be better.

Now, there’s no way for us to tell what species of lactic acid bacteria we are adding to our brews when we do this in our kitchen. But if you look up the most common types of lactic acid bacteria, you’ll see that they are almost all probiotic and beneficial to human health in some way, so it’s hard to see how you could go wrong.

Based on the paper that talked about adding chopped cabbage, this is how to do it in your own kitchen:

Make up a batch brew of kombucha using your normal recipe, but put about a cup of finely chopped cabbage into the jar with the tea (assuming you make up a batch of about a gallon). Leave it to ferment as usual for a week, or as long as it takes to get a good healthy daughter scoby. It is late winter here in the Southern hemisphere, and our scobys are very sluggish at the moment! Fish out the scobys (mother and daughter), and set aside a cup of the kombucha liquid. Discard the mother and the rest of the liquid. (unless you like the flavor, in which case, drink it as usual) Set up another batch using the new daughter scoby and the cup of reserved kombucha liquid. You’re good to go. This daughter should have soaked up and incorporated some lactic acid bacteria from the chopped cabbage, and your kombucha will be lacto-fermenting from now on.

For adding milk kefir, do basically the same, but I’d use a tablespoon or two of milk kefir whey in place of the cabbage. (Strain the kefir through a cheese-cloth to get a mostly clear liquid – that’s the whey).

And there you have it. All about lactic acid bacteria, how they improve your kombucha, and how you can make sure you’ve got some.

Happy Brewing!

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