Among all the different types of bacteria that can infect a beer, Bacillus is one of the lesser-known, less-discussed offenders, despite it being pervasive throughout the brewery. Luckily, it’s also not as detrimental as some of the other usual suspects.
Note that in this context we’re not talking about Lactobacillus—a more persistent microbe with which craft brewers tend to be familiar, whether you’re using it intentionally for acidification or trying to avoid it at all costs.
Bacillus, meanwhile, is unlikely to cause off-flavors in your finished beers—I’ll explain why below—yet it is widespread around the brewery, especially during the warmer summer months. As with all microbes that affect brewing, you should be aware of Bacillus and know when it could become an issue.