Been making my own fermented foods now for quite some time (beer, pickles, etc) and I'm looking to take it to the next level.
Specifically I want a strain of bacteria that will maximize production of vitamin K2 MK7 for a soup I have been making in order to help my mother fight breast cancer. Currently I have just been throwing some miso paste into the soup after it cools a bit.
I know natto (bacillus subtilus) is supposedly the highest source for this - does anyone know where I can get the starter culture and if it would ferment in a soup base? How long would I need to let it go for?