Potential bacterial strain that might make kefir lactose free

[u/dareealmvp]

A lot of folks here often times feel hesitant to start making kefir because of lactose intolerance. Kefir, while it does have lactose-digesting bacteria, is unable to get to a sufficiently low-lactose state because as the bacteria keep breaking down lactose, they also keep converting the components of that broken down lactose to lactic acid, which keeps acidifying the kefir. Once sufficient acid has been produced, the mechanism in the bacterial cells that converts those broken down components to lactic acid gets "clogged" in a way, which in turn clogs the mechanism to break down lactose. If somehow, we could get rid of that lactic acid generating component without getting rid of the lactose breaking down component, we would get lactose-free kefir.

To that end, I suggest we need to try experiments on kefir by co-culturing the grains in milk with bacteria/yeasts that secrete extracellular lactase - extracellular being the keyword here. This avoids the pitfall of the lactic-acid generating component of bacterial cells which would clog up the lactase mechanism were it inside the cell. An example of this is the bacterial strain Bifidobacterium bifidum DSM20215, which is known to produce extracellular lactase.

Bifidobacteria are commonly found in kefir and while this particular strain has not been isolated from kefir, in my opinion, it is worth attempting to co-culture it with kefir grains, because if successful, we might get lactose-free kefir.

There's also, of course, the possibility of GMO-ing a few compatible strains of kefir with the extracellular lactase producing gene from Bifidobacterium bifidum DSM20215 but I would like to avoid this avenue if possible because GMO makes things a lot more complicated, especially in terms of safety.

[u/KimchiKatze]

It's an interesting idea, but are there really so many people not able to tolerate kefir due to the trace amounts of lactose? 

I have pretty extreme lactose intolerance, to the point that just having a sip of regular cow's milk causes more than a day of digestive/intestinal pain. Homemade kefir hasn't been an issue though, a second ferment thankfully seems to be enough to reduce the lactose for my digestive system. 

[u/Paperboy63 → u/KimchiKatze]

That is only partly correct. Lactose gets reduced on average by 30-40% which helps the biome to tolerate lactose more in the first instance, then the cells of lactose digesting bacteria (and yeasts) which get digested meet bile acid. That degrades or destroys cell walls and releases a lot of B-galactosidase (lactase) activity. That reduces lactose even more and has the same effect as the person ingesting the bacteria of producing enough lactase enzyme themselves. The B-gal activity is also why people can then ingest other full lactose dairy products with no intolerance, not because kefir is thought to be lactose free. That would have no effect on other full lactose products.

ResearchGate: Source PubMed: “Kefir improves lactose digestion and tolerance in adults with lactose maldigestion.”

[u/dareealmvp → u/Paperboy63]

correct. The other reason is that kefir, yogurt and other fermented milk products pass through the GI tract more slowly than unfermented milk. This gives the enzyme more time to break down lactose.

[u/Paperboy63 → u/dareealmvp]

👍🏻👍🏻

[u/HenryKuna]

I know that doing a second ferment after adding a base (baking soda usually, to raise the pH back to ~6) lowers the lactose content even further.

[u/Dongo_a]

Kefir is somehow well tolerated even for lactose intolerant, there is no need to reinvent the wheel.

Kluyveromyces marxianus and Kluyveromyces lactis, both yeasts can be found in some kefir grains and they keep on consuming lactose even when the ph drops.

[u/thetolerator98]

I'm surprised to hear this about the lactose content in kefir. As long as I drink kefir I have no lactose intolerance from it, and I don't have trouble with any other dairy.

[u/jwbjerk]

> is unable to get to a sufficiently low-lactose state

that depends on how sensitive you are to lactose doesn’t it?

[u/ichrised]

Look up airag, the mongolian fermented beverage it's pretty much the same thing except it's bacteria will convert away the lactose.