Brewer's Yeast OK with MAOI
Did you ever find an answer to your question? I found a scientific refereed journal article, stating that brewer's yeast is fine with MAOIs. The information is on the bottom of the second page of the article. It's actually quite helpful, and discusses how different foods become off-limits, and how some of that was not good science.
It won't let me post the link, but you should be able to google the title and authors:
Journal of Food Composition and Analysis 19 (2006) S58–S65
Tyramine in foods and monoamine oxidase inhibitor drugs: A crossroad
where medicine, nutrition, pharmacy, and food industry converge
Beverly J. McCabe-Sellers, Cathleen G. Staggs, Margaret L. Bogle