I want to make a bread with a stout in it for extra flavor. The stout will replace most of the liquid content of the bread and I am worried whether it will kill the yeast due to the alcohol (4% volume) content of the stout.
Yeast, depending on the strain, can typically sustain in alcohol in concentrations of up to 14-18%. Some strains can actually go higher. (I personally keep a champagne yeast on hand for homemade root beer and ginger ale that goes to about 18%). Typical bottled beer runs to about 6%.
Once started the fermentation process, at room temperature, is only slowed or stopped by CO2 build up or starvation, until the alcohol reaches toxic levels. Given the portion of beer to the overall volume in beer bread recipes, the abundance of food for the yeast and the relatively short period allowed for rising none of these factors should inhibit the yeast.
In short, the environment in your dough will reach nowhere near 'toxic' levels during the rise.
Even after reading a bunch of peer reviewed articles, I was unable to find a definitive answer to this question. The closest thing to a direct answer I found that in this Serious Eats article focused on pizza dough additional ingredients, dbcurrie says:
[Beer] Creates a supple dough. Depending on the recipe, beer can be substituted for just some—or all—of the liquid in a bread recipe.
There was a cached google reference to Shirley O. Corriher in Fine Cooking saying that "eventually" the alcohol produced by yeast as a byproduct of its metabolism would inhibit further activity. However, no level or percentage was given.
Historically, we know that bread yeasts were a byproduct of the beer brewing industry, so they must be able to tolerate at least up to beer levels of alcohol. While it may possibly be in the range where their activity is retarded, they obviously were not killed as the brewer's yeast could then be reused in the next batch, and given to bakers.
Given that the ingredients in a single loaf of bread cost very little, and that one beer is not a huge investment, I would encourage you to try it and see.
Wyeast lists alcohol tolerance at 11%. So I would have no worries about a normal strength beer causing problems.
I have been experimenting with yeasted (not baking soda) beer breads for weeks now. The flavour of a long fermented, yeasted beer bread blows anything you do with baking powder totally off the table. I'm experimenting with 30-50% of my hydro content beer and with fermetantion times between 4 and 12 hours. And no, the yeast is just fine.
All produce different tastes. At the cost of salt, a beer and flour & yeast for a loaf, you can experiment too until you find your best taste.
PS: Different Lagers & Pilsners I've tried thus far all produce similar flavours. The only thing that tasted radically different was a Craft IPA. But then THAT is to be expected!
I use Guinness Extra Stout in my Beer-Cheese-Jalapeno Bread, substituting beer for water one-to-one. Comes out terrific. I use a bread machine. Latest loaf made this morning.