When smaller breweries are in their early days, most ferment their beers using commercially available yeast strains. Perhaps the strains are favorites from the founder’s homebrewing days, or perhaps the brewers are using several strains chosen for a wide variety of beers.
At some point, however, as the brewery matures, it often adopts one or more house yeast strains, and there are many sound reasons to do so: House strains can save a brewery money, increase cellar throughput, and help create better, more consistent beers.