I am curious as to whether anyone has ever done the bulk of fermentation with one strain of yeast, and then added another strain for bottle conditioning. I know all the beginners manuals say “never combine different strains of yeast, check the batch numbers” etc. But this golden rule may just be a training wheel I’m ready to do away with.
I know Belgian breweries that make big ales tend to ferment with one yeast and then condition with another more neutral flavoured yeast. This would make sense if you wanted a flavour imparting yeast for fermentation but a powerful yeast that will give good attenuation while conditioning. (These styles of beer tend to have very low-carbonation anyway so further attenuation in the bottle is unlikely to cause bottle explosions.)
After prolonged ageing and lagering/crash-cooling/cold-storing, there would be little original yeast left active anyway. Is there some kind of danger of yeast interaction??
I don’t feel like you gain very much of anything by fully fermenting a beer with one yeast, and bottle conditioning with another, with the possible exception of bottle conditioning with Brettanomyces.
There’s just not really enough fermentables in 4 or 5 ounces of bottling sugar to make that much difference in the beers flavor. I’d caution against bottling with a more attenuating/alcohol tolerant yeast just due to the possibility of making beer grenades if the conditioning yeast decides to start munching on some of the sugars left over by the primary yeast.
I think multiple yeast fermentations are a very under utilized tool in the homebrew community. The resulting beers can be very satisfying, and truly unique. Also, it’s surprisingly easy to bury the character of a mild yeast by using a more colorful yeast in the same ferment. The trick is to use two (or more) yeast that complement each other, and then bring their flavors into balance. It’s not easy, but it can be done.