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Specifically, I'd like to find out how to grow ME-3 L.Fermentum (DSM 14241) at home without any fancy equipment. What food does it need? Sugar? Lactose? Something else? At what temperature does it grow? How fast? How can I generally find answers to these questions? ME-3 is not the only strain I'd like to grow. I know ME-3 grows in milk, but that doesn't work for me. Can I grow it in vegan milk? In just water with sugar? I'm even more interested in finding ways to find out the answer to these questions. Where would you look to answer this? I tried to google it but it's hard. Is there not some cool data base that has growth conditions for every known strain?

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  • $\begingroup$ Why not grow it in milk? Bacteria aren't vegan... $\endgroup$
    – MattDMo
    Jan 19, 2023 at 17:40
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    $\begingroup$ Another thing to consider is that, as an intestinal bacterium, L. fermentum is almost certainly anaerobic, meaning you need to culture it in conditions with little to no oxygen in the atmosphere. While not impossible, this is rather difficult to accomplish at home. $\endgroup$
    – MattDMo
    Jan 19, 2023 at 17:52
  • $\begingroup$ It's not anaerobic. ME-3 may not be vegan, but I am ;-) . That's why animal milk doesn't work for me. $\endgroup$ Jan 21, 2023 at 19:28
  • $\begingroup$ I saw a paper where they were culturing it under anaerobic conditions. that's why I made the comment. Doing more research, I see that it's a facultative anaerobe, not obligate. $\endgroup$
    – MattDMo
    Jan 21, 2023 at 19:31

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If you do not have any experience culturing microbes do not attempt this.

You are very very likely to contaminate your culture with things that could make you very sick or even kill you. Pathogenic microorganisms are part of our natural microflora and are a significant cause of hospitalizations throughout the world as a result of food poisoning. For this to work you would need some skills in both identification of microorganisms (to make sure you have the right one) and in sterile technique. Growing specific microorganisms is NOTHING like making yogurt or beer with high inoculums of culture organism that suppress the growth of contaminants, or even like starting a sourdough starter, where you have a relatively low inoculum but the right the culture to the right bacteria/yeasts.

This would mean that you need, at a minimum, a microscope (with 40-100x objectives; for identification purposes), slides, a differential bacterial stain (e.g. Gram stain), sterilization equipment (for preparing media; this could be a pressure cooker), media and an incubator with the right conditions.

This organism needs some carbon, nitrogen and a number of elements to grow happily. I don't think you will be able to do this at home easily; it would require quite a bit of experimentation and you are likely to grow something nasty as a contaminant before you get a decent culture of your target organism.

The American Type Culture Collection recommends Medium 416 for growth of Lactobacillus group organisms. This medium is comprised of lactobacillus MRS medium from BD and contains:

Proteose Peptone No. 3 10g/L, Beef extract 10g/L, Yeast extract 5g/L, Dextrose 20g/L, Polysorbate 80 1g/L, Ammonium Citrate 2g/L, Sodium Acetate 5g/L, Magnesium Sulfate 0.1g/L, Manganese Sulfate 0.05g/L, Dipotassium Phosphate 2g/L.

Now this might look like a scary list of things, and fairly unobtainable, but beef extract is essentially beef broth, and yeast extract is hydrolyzed yeast. The Polysorbate is an emulsifier used to help solubilize the ingredients and as a carbon source. I don't know if it is obtainable outside of a laboratory setting. The other chemicals may be hard to find too, though citrate = citric acid (fruit acids, you can buy this in a supermarket), acetate = vinegar/acetic acid. Manganese and Magnesium might be obtainable as health supplement pills, but you would need to work out how much is in a pill and do some calculations to convert. As a bonus, supplement pills often contain calcium phosphate as a bulker/tableting agent. For the peptone you might be able to substitute milk powder or "protein shake" powder. You would need to know a bit of chemistry to for the citrate -> citric acid, acetate -> acetic acid, and etc. conversions.

The last problem is that the ATCC recommends that the organism be grown in 5% CO2 at 37 degrees Celsius (98.6 F). This requires a sealed incubator box, with a means to get the CO2 in there. You might be able to achieve this by chemical means, reacting some chalk (calcium carbonate) with acid, but it would take some experimentation to do so effectively. It should grow at lower temperatures too, but it will grow slowly, if at all. I don't know if the CO2 is a requirement or just something that helps with the growth. This is not an obligate anaerobe as suggested in the comments, but can grow anaerobically too (facultative anaerobe).

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  • $\begingroup$ I don't know... I've made DIY yoghurt with all sorts of probiotics countless times and never got sick from it. Now I want to do the same with ME-3 yoghurt. It doesn't have to be a 100% only the ME-3 strain, i.e. it doesn't need to be sterile. As to avoid food poisoning, I just add some other standard yoghurt strains to the mix, e.g. L.Bulgaricus (found in most yoghurts) to create a stable environment. I've done this many times with cow milk. But now I want to do it without milk, i.e. vegan yoghurt. That's why I want to know what ME-3 (and other's that I want to grow as well) need to be happy. $\endgroup$ Jan 21, 2023 at 19:23
  • $\begingroup$ The ATCC link leads to a a different L.Fermentum strain. Is this not strain dependent? ME-3 is DSM 14241, but somehow I can't find it in the DSM (why?). HOw would you find out the ATCC number of ME-3 ? $\endgroup$ Jan 21, 2023 at 19:26
  • $\begingroup$ An MRS medium doesn't work for me, since my goal really is to make a vegan yoghurt that I can eat. $\endgroup$ Jan 21, 2023 at 19:27
  • $\begingroup$ Also, I'm particularly interested in a general approach as to how I can answer these questions myself such I don't always have to ask this forum. I struggle with just googling it since I don't know what websites to go to. I take it from your answer that culture collections are the place to look for answers? Here I often struggle to find the type number of that strain. E.g. it took me a lot of googling to find out ME-3 is DSM 14241. Is there not some great data base that has everything that there is to know about all known strains? What temperature, pH, salt content etc do they tolerate? $\endgroup$ Jan 21, 2023 at 19:32
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    $\begingroup$ @AntonRodenhauser if you have an inoculum (i.e. the strain itself) this makes it a whole lot safer to do. Trying to isolate is a lot harder. If you do inoculate with other bacteria you will likely result in those dominating the culture, especially if they are ones that are already selected for growth in those media. You would have to do some relative growth rate experiments to work out how well it would work. $\endgroup$
    – bob1
    Jan 21, 2023 at 20:53

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