Problem:

In a book about post-war Japan (Embracing Defeat, Dower) the author mentions a process for making sawdust at least partially edible, so it could be used in recipes in a 1:4 ratio with flour for cooking. The author says the sawdust was "fermented," as I recall.

Question: Whether this is anything more than marginally possible.
After all, kimchee, yogurt, beer, and other fermented foods aren't necessarily easier to digest.

Question: Is there a fermentation process involving bacteria that break down cellulose that might make wood even slightly nutritious?

My impression is that in forests the process of breaking down wood does not initially involve bacteria but other microorganisms; on the other hand, ruminants such as cows use bacteria to help them metabolize.

Explain fermentation process involving bacteria that break down cellulose.