The good bacteria in sauerkraut are important to our gastrointestinal health. We have eaten lactic acid bacteria on a daily basis for most of human history and it is only in the last fifty years that we have moved away from this.
And it is within the last fifty years that we have seen an enormous rise in gastrointestinal health problems. Many doctors believe the two are connected.
In one study of bacteria collected from four commercial sauerkraut fermentations, a total of 686 bacterium were discovered1 although not all of them are in the sauerkraut at the same time.
This means if you're someone who makes your own sauerkraut and eats from it as it is fermenting, you will be getting a continually changing supply of lactic acid bacteria.
It is well established that strains from within the same family can differ in their health promoting effect so this enormous diversity is possibly the strongest of the benefits of sauerkraut.
Bacteria found included:
Leuconostoc mesenteroides is the bacteria that gets the fermentation started by changing the sugars in the cabbage (glucose and fructose) to lactic acid, acetic acid, ethanol, CO2, and other flavor compounds.
As the process continues the production of the acids lower the pH of the sauerkraut and stop harmful bacteria from getting a foothold.
Eventually the L mesenteroides will die as conditions within the fermenting cabbage "brew" become unfavorable for its growth.
The CO2 makes the ferment airless and this encourages the growth of the lactic acid bacteria such as L plantarum who enjoy this condition and can exist in a highly acidic environment.
L plantarum becomes the dominant species of good bacteria after the first week of fementation and by 2 weeks will sometimes be the only species present. I say "sometimes" because each brew of sauerkraut differs. That's the beauty of it all!
It is only through the proper succession of these lactic acid bacteria that the quality and saftey of the sauerkraut can be assured.
Lactobacillus plantarum is the species that you're likely interested in the most. Some strains of this useful bacteria are probiotic and can be found in supplements and a variety of foods.
1. Vethachai Plengvidhya, Fredrick Breidt, Jr., Zhongjing Lu, and Henry P. Fleming. DNA Fingerprinting of Lactic Acid Bacteria in Sauerkraut Fermentations. Appl Environ Microbiol. 2007 December; 73(23).