Do you think most people know that Brewer's yeast is alive?
If Walker wanted to discredit your essay. He could give a sound bite like:
“Ok, yes, yeast. You’re right, but that’s not something most people consider relevant to sleeping rhythms. Haha. The essay is nitpicking minor technicalities but on a whole my research is unblemished.”
If I were his PR rep, I’d advise as such. You’re essay is too good to be vulnerable like that.