Natto makers - I'm looking to make natto with plenty of "neba-neba". This is natto's characterist slime/string/goo. I read somewhere online that adding some japanese yam during the inoculation stage helps, and if true, I wonder if this provides the natto bacteria with 'special' nutrition, and I wondered if that would be some kind of sugary starch?

I've also read online (natto dad blogspot website) that using store bought natto as a starter makes better natto than using pure spores as a starter. This makes me wonder if there is a connection between this, and using an added ingredient such as yam. Can anyone provide any additional information about this please? Thanks a lot.

  • I saw a documentary on NHK a while back, and they interviewed a researcher at a company that made natto ... and the specific bacteria cultures used ... so although wild fermentation might solve the problem, it might be better to look for a commercial starter that specifically claims to have the characteristics you're looking for (flavor, firmness of the beans, stickiness, etc)
    – Joe
    Jul 9, 2019 at 15:16
  • found it ... youtube.com/watch?v=CN1_rlq3RzY . The factory scene starts at 19:08
    – Joe
    Jul 9, 2019 at 15:20

1 Answer 1


In order to make natto we need to eliminate starter cultures - same goes for making kombucha, yogurt, sauerkraut etc. Which came first the chicken or the egg? At some point in time we need to become self sufficient so that if the time comes where we can't access these said cultures, we can still produce these fermented foods.

The Japanese used Rice stalks. There is nothing inherently special about rice stalks that separates them from other vegetation because all vegetation contains Bacillus subtilis. you could use a corn stalk, grass clippings, dried edible weeds, or even a bale of hay. As long as it's dead and dried out and not poisonous anything is fine; you could use dried out cabbage leaves, etc. Right now I'm using dried banana leaves. (not banana peelings).

The rice stalk or whatever you choose to use is boiled for around 10 minutes. It is very important that this boiling is done at the threshold of boiling. You might be thinking that this would be for sterilization to eliminate foreign invaders from taking over the ferment, but in actuality, it is this temperature that wakes up the Bacillus subtilis. I personally don't care for the idea of boiling because it imbibes the dried out vegetation. I find even after I remove all the water possible from the beans, the dried vegetation will still be saturated from the residual leakage. That is inevitable, so I live more dangerously making my natto just like it was made the very first time it was made by the Japanese. If you're interested in considering this process proceed at your own risk.

In order to obtain a good amount of neba I apply the vegetation that I'm using. I use a pressure cooker to cook the beans and as soon as they are done, I get those beans out as soon as possible. I make sure I drain them completely. I want no standing water; this is all done very quickly so as to keep the beans as hot as possible.

As soon as all water has been removed, a bed of the dried vegetation has already been laid down in a large plastic or glass container (like one you would make lasagna in).

The hot drained beans are poured into this container on top of the dead dried vegetation that entirely covers the bottom of the container. The heat from these beans in contact with this vegetation is what wakes up the Bacillus subtilis. Immediately afterwards another layer of dried dead vegetation is put on top with the lid put on top and almost sealed (I leave it slightly open in one corner). It is now placed inside a huge styrofoam cooler that already has a standard heating pad in it turned on and it is heating up a similar sized container of water. The container of beans rests on the container of water so that the heating pad is not directly in contact with the beans. The lid to the styrofoam container is closed and it will remain around 100°F to 108°F for 24 hours. The closest thing to store bought natto will be made with soybeans or garbanzo beans; although a lot of other beans can produce natto, the flavor will vary. Lentils don't make natto.

  • This answer seems fairly knowledgeable, but is hard to read; I have suggested an edit to make it easier to understand.
    – SuperWild1
    Jul 8, 2019 at 2:29
  • Welcome to Seasoned Advice, by the way.
    – SuperWild1
    Jul 8, 2019 at 2:31
  • 1
    Very good info on how to produce natto, but which part of this process improves the neba-neba amount? you should edit your answer to explain that better.
    – Luciano
    Jul 9, 2019 at 10:12
  • I cook and eat a LOT of Japanese foods and lived in Japan for a total of 15 years from the time I was a little boy...back and forth to the USA. The one single food I have never been able to acquire an affinity for is natto! Happy others like it, but for me, it is awful stuff. The answer above was detailed and accurate. Well done!
    – SittingElf
    Jan 16, 2020 at 11:49

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