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Homemade Japanese Natto Beans

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Japanese natto is made by fermenting soybeans using a very specific spore that creates a nutty, delicious food that some might even call slimy. But if you've had it, you know that Japanese natto is slimy in the best possible way.

1 hour

48 hours

6 cups


Natto Starter

Tempeh & Soy Natto Spores

Natto Starter


Use natto starter to make real Japanese natto at home! Ferment soybeans with these natto spores to make traditional natto or use nearly any bean of your choice.

Each pouch contains 4 packets of natto starter culture. Each packet yields 6 cups of natto.



  • Be sure the entire process, including all utensils, pots, cheesecloth, etc. are as sterile as possible. (Boil utensils for 5 minutes prior to using.)
  • The fermentation process requires the natto starter to be kept at approximately 100 - 105 F degrees for 22 to 24 hours. Ovens with a low-temperature setting can be used, as can large cube-shaped food dehydrators.
  • Natto spores are quite odorous while fermenting, and you may want to isolate the natto during the fermentation time.

Download all our Lacto-Fermentation Recipe Book today and start cooking excellent meals for your friends and family! Learn how to make your own delicious and healthy Japanese Natto Recipe!



  • Aluminum foil
  • Non-reactive pot (i.e., stainless steel, enameled, etc.)
  • Large stainless steel spoon
  • Colander
  • Casserole dish



  1. Wash the soybeans and soak in 6 cups of water for 9 to 12 hours (longer soaking time recommended for colder months) to get them ready for fermentation.

    Soybeans for Japanese Natto is soaked in 6 cups of water.
  2. Drain the soybeans from the soaking water. Place beans in a large pot, fill with water and boil for 2-3 hours, checking every half hour or so. You want them to be tender but not mushy so that the spores have plenty of moisture for fermentation, but the final result is still firmly textured.

    Japanese Natto beans are tender.
  3. Rinse or dunk a colander, cooking spoon, and casserole dish with boiling water to sterilize. We want to make sure that only the right organisms thrive in our fermented soybeans!

  4. In the sterilized colander, drain the cooked beans and place in the sterilized casserole dish. Turn oven light on so it preheats to 100 degrees F.

  5. Stir in the natto powder with 3 Tbs. boiled and cooled (for sterilization) water. While the beans are still warm, pour the natto spore packet over the beans. Stir the beans carefully using the sterilized spoon.

  6. Spread the beans in a ~1 inch layer in the casserole dish. If at any point in the process the beans spill on the counter, etc., discard those beans to prevent contamination. It's critical to maintain the purity of our ferment for the best final product.

  7. Tightly cover the casseroled dish with aluminum foil. Poke pin holes in the foil, placed 1" apart. The natto spores need a little oxygen and darkness for idea growing conditions.

    Casseroled dish with poked pin hole aluminum foil
  8. Place the covered casserole dish in the oven, dehydrator, or other warmer and allow the natto to ferment for 22 to 24 hours, being sure to keep the temperature at a steady 100 degrees F. When you see a whitish film and smell an ammonia-like aroma coming from the beans, that's how you know they're done fermenting.

    Natto beans are done fermenting.
  9. When finished, let the Japanese natto cool at room temperature for 2 hours. Remove aluminum foil and store in covered containers in the refrigerator at least overnight for best flavor and stringiness. Your natto will last for about a week in the refrigerator.

Smaller portions of finished natto can be stored in the freezer and thawed for later use.


Cultures for Health is here to make your natto fermenting journey as easy as possible. We have plenty of information about fermenting soybeans, and we have quality natto spores you can get today.

Our Natto Spores allow you to make authentic Japanese natto at home! You can ferment soybeans with these spores to make traditional natto or use nearly any bean of your choice for some really interesting custom natto experiences! 

Click here to get your hand on our incredible Natto Spores and start making your own food now!


Want to start making your Japanese Natto at home? Download all our Cookbooks today to get started!


download lacto-fermentation guide and recipe book


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