I did this years ago and it seemed to work, but n=1. It took two cycles of antibiotics and intentional introduction of "good bacteria" before I landed on something that seemed to fix most of my food intolerances. Didn't seem to have any impact on anxiety.

I learned later that this is pretty dangerous to attempt, since you're very likely to give yourself c diff or some other infection and end up with persistent IBS before you land on a good microbiome.