Let’s take a moment to clear up an issue that seems to confuse many people: the issue of time in microbial fermentation and reproduction. Time plays a crucial role, for instance, in whether or not you obtain the sorts of outsized effects we often experience with our various fermentation projects such as yogurt-making.
Recall that, unlike humans and other multicellular creatures, microbes don’t engage in sexual reproduction, but propagate their species through so-called asexual reproduction, a process that does not involve differences among male and female microbes, but essentially means that one microbe becomes two, two becomes four, etc., by recreating themselves with the same (or nearly so) genetic code. Offspring are therefore generally indistinguishable from the “parent.”
For many microbes, this process typically requires 1-4 hours, i.e., the time required for a microbe to recreate itself and becomes two. Each microbe recreates its genetic code and various other parts, then separates into two. Our favorite microbe, Lactobacillus reuteri, requires 3 hours to recreate itself at 100 degrees F, the temperature at which this microbe doubles at its maximum rate—lower the temperature and reproductive frequency is decreased, higher and the microbe can succumb to heat and die (especially at 108 degrees F and higher for this species). This is why we are mindful of the temperature at which we ferment microbes as yogurt or other fermented food. Temperature is therefore important in determining the rate at which proliferation will occur. That’s easy: just set the temperature that has been determined to be the optimal for reproduction (that I provide in my recipes in this DrDavisInfiniteHealth Blog, Inner Circle, Super Gut book recipes).
We also have to factor in time. Remember the kids’ riddle–Which would you rather have: $1 million or a penny that doubles every day for 30 days? Kids always choose the $1 million, of course, not expecting that a penny could achieve any substantial growth. But it does: $5.5 million by day 30. Look at the curve of growth of money: the really big increases in money don’t occur until around day 26 or 27, meaning the increase in money in the preceding 26 days is relatively minor.
If a microbe reproduces every 2 or 3 hours, it means that the 4 hours of fermentation/reproduction typically used in commercial manufacturing of yogurt yields almost nothing. If a starting microbe was a penny: $0.01, $0.02, $0.04 . . .three doublings—not very interesting. It’s not until the last few days of the month when really interesting increases in money develop, corresponding to hours 33 or longer in microbial reproduction. In commercial manufacturing of yogurt and other fermented foods, time is money, so they abbreviate the amount of time as much as possible. In the case of yogurt, they therefore add carrageenan, gellan gum, xanthin gum and other thickeners to compensate for the lack of microbes and metabolites and artificially thicken the product.
Why is this important? We are trying to influence trillions of microbes living in the human gastrointestinal (GI) tract. If you introduce 100,000 or 1,000,000 or 10,000,000, or 100,000,000 or even 1,000,000,000 (1 billion) new microbes, you are unlikely to exert a substantial effect when there are many trillions—1,000,000,000,000—of microbes residing there already. In other words, Because most commercial yogurts contain a few hundred million, you simply cannot expect much health benefit. We therefore allow enough doublings that we obtain big, big numbers. (There is a limit, however, and the several runs of flow cytometry we’ve run on yogurts fermented more than 36 hours and up to 48 hours yield no further increase in live microbes but an increase in dead microbes.) And, of course, unlike the ho-hum bacterial species used to make conventional yogurt, we choose species that yield interesting effects.
Using my 36-hour method of fermentation that, for L reuteri allows 12 doublings, we obtain around 250-260 billion counts per 1/2-cup serving. I believe that this is part of the reason why we are having so much success in generating big effects.