I was delighted to run into Sandor Katz Thursday evening while we were setting up our display at the Weston A. Price WISE Traditions conference! He is one of the top experts in fermentation, and I promised a customer I would ask him a question about natto spores and where they come from.
Turns out the spores exist naturally on all soybeans that haven’t been pressure-cooked! We get our nattomoto from a Japanese producer of high-quality organic Asian foods, but if you wanted to make your own, you could!
Sandor said that if you make Tempeh, and let the mold develop thoroughly, the nattomoto spores will grow. You could then dry the mold and grind it into a fine powder for your own natto. Thank you Sandor!