Published Tuesday, July 13, in the journal Biochemical and Biophysical Research Communications, the study showed that unheated natto extract degraded the receptor-binding domain (RBD), a key region of the spike protein that studs the outer surface of SARS-CoV-2.

The RBD is especially important because the virus uses it to anchor to a receptor on the surface of certain cells before infecting them.

Moreover, the researchers confirmed that the unheated natto extract had the same effects on the RBD of some of the mutated strains of SARS-CoV-2, particularly the alpha variant. This variant was first detected in the United Kingdom in September 2020. It was then detected in the U.S. three months later.

Natto extract degrades key region of SARS-CoV-2 spike protein

Natto is a traditional Japanese dish made by fermenting soybeans with Bacillus subtilis, a bacterium typically found in soil and vegetation.