This is the first article of a series we will call “The Natto Stories,” we hope you enjoy it.
Let’s start with a natto quiz!
Q：What is the raw material to make natto?
It was an easy one.
The answer is “natto bacteria and soybeans” (* limited to itohiki natto).
Q：Is there any raw material other than soybeans suitable to make natto?
There are several soybean varieties, black soybeans, green soybeans, green soybeans, edamame, etc.
Then, is it possible to make natto with beans other than soybeans? The short answer is no.
Thirty years ago (when I was still a college student), I experimented with what would happen if I planted natto bacteria in various beans. I remember testing red beans, pinto beans, chickpeas, lentils, etc.
These were my results…
- The characteristic natto strings were not formed.
- B. subtilis did not grow properly.
- The fermented product had odor.
It was remarkable to obtain all those negative results together no matter what kind of beans I used.
Why is it not possible to make natto with beans other than soybeans?
Let’s analyze the culture media.
In terms of plant taxonomy, soybeans belong to kingdom Plantae, subdivision Spermatophytina (phanérogames), superorder Rososanae, order Fabales, family Fabaceae, genus Glycine Willd, species Glycine max.
Green soybean and black soybean are part of the genus Glycine. However, lentils and other legumes tested belong to different genus and species. In other words, they are biologically different from soybeans.
- Bacillus subtilis can utilize only specific components in soybeans for fermentation.
- Beans different from the Glycine genus contain components that interfere with the growth of Bacillus natto, hindering fermentation.
I theorize that soybeans have unique ingredients essential for successful fermentation. However, there is no available research to answer this speculation.
Let me tell you a well-kept industrial secret.
When the Bacillus natto ferments soybeans into natto, it also produces numerous functional ingredients such as nattokinase, vitamin K2, polyglutamic acid, Etc. Many companies commercialize those ingredients, not the natto itself. The best growing medium for producing B. subtilis on an industrial scale is still soybeans.
The serendipitous encounter of Bacillus natto with its best culture medium, soy, hundreds of years ago gave us natto!
Natto is a fermented food full of mysteries.
Sonomono Inc. Academic Advisor
Mr. Ogasawara graduated from Kumamoto University Graduate School of Medical Education. He actively researches and develops functional raw materials such as nattokinase. His professional experience as a researcher over more than 35 years includes microbiology, fermentation, enzymology, and bacterium.