A beer fermented with Brettanomyces alongside acid-producing bacteria such as Lactobacillus and Pediococcus, producing both the leathery, fruity funk of wild yeast and a genuine bacterial tartness. It sits between a clean Brett beer and a full-blown sour ale: more acidic than a Brett-only beer, but defined as much by yeast-driven complexity as by sourness. Color, strength, and base beer all vary widely, since the category is built on what the mixed culture does rather than on any fixed recipe.
In the glass
Origin
Brettanomyces was first isolated and named in 1904 by Niels Hjelte Claussen at the New Carlsberg brewery’s laboratory, who identified it as the organism behind the character that developed in aged English stock ales; the name means “British fungus.” Long before that, the same wild yeast and souring bacteria had worked together in Belgian lambic and Flanders red beers, where mixed populations of Saccharomyces, Brettanomyces, and lactic bacteria ferment and mature wort in wood. American craft brewers drew directly on those traditions as the wild and sour beer movement took shape in the early 21st century, building deliberate house cultures that combine Brett with bacteria rather than treating either as a flaw. Breweries such as Jester King in Texas, which ferments with a culture of brewer’s yeast plus native yeast and bacteria gathered around its Hill Country site, and Crooked Stave in Colorado made mixed-culture fermentation the foundation of their identity rather than an occasional experiment.
Notes
This category is best understood by what sits on either side of it. A Brett beer leans on wild-yeast funk and stays close to dry rather than sour; an American sour ale can be cleanly tart from bacteria alone. A mixed-culture Brett beer needs both at once — the leather-and-fruit complexity of Brettanomyces and a real lactic or acetic acidity from bacteria working in tandem. Because the cultures evolve over months or years in barrels and foeders, no two batches mature identically, which is why blending across vessels is central to the craft. The results range from pale and tart farmhouse-style ales to dark, fruit-laden, deeply funky beers.
Defining examples
Jester King Le Petit Prince·Jester King Noble King·Crooked Stave Surette·Jolly Pumpkin Bam Bière·Allagash Coolship Resurgam