Microbes: The Real Stars Of Sour Beer Production

men tasting beer in production

Most beer is produced through the use of yeast, which ferments the sugars in malt to produce alcohol. However, for sour beer production, this process is done through the use of bacteria. These bacteria, a kind of microbe, play a vital role in ensuring that the beer is sour. To produce sour beer, brewers must first create a bacterial culture. This culture is then added to the beer during fermentation. 

The bacteria consume the sugars in the malt, producing lactic acid and carbon dioxide. This gives sour beer its characteristic tart flavor. In addition, the bacteria help to preserve the beer and prevent it from spoiling. Without microbes, sour beer simply would not exist. There are a variety of different microbes used in sour beer production. Here's what you should know about brewery microbiology.


Saccharomyces is the genus of fungi that includes many species of yeasts. These microorganisms are responsible for alcoholic fermentation in beer brewing. In fact, the word "saccharomyces" comes from the Greek words saccharon, meaning "sugar," and myces, meaning "fungus."

While most beer is made with Saccharomyces cerevisiae, a few beer styles, such as lambic and gueuze, are fermented with a mix of yeasts that includes other members of the Saccharomyces genus. These other species can contribute to the flavor and aroma well known in sour beer production.

Saccharomyces cerevisiae is a single-celled organism that reproduces by budding. When beer brewers talk about "yeast," they usually refer to this species. It is sometimes also called "baker's yeast" because it is used to leaven bread.

This microbe thrives in warm, oxygen-rich environments and can tolerate high concentrations of alcohol. It is used to make many different types of beer, including ales, lagers, and wheat beers.


Brettanomyces, often called "Brett," is a type of yeast that is commonly used in the beer production process. Brettanomyces is known for its ability to produce sour and funky flavors. Brettanomyces is also used in the production of wine, cider, and mead. While Brettanomyces is not technically bacteria, it's often lumped together with bacteria when discussing brewery microbiology

Brettanomyces can be a difficult yeast to work with. It is known for producing off-flavors, and can be difficult to control. However, Brettanomyces can produce some of the most delicious and complex fruit beer flavors when used properly. Brettanomyces is often used in conjunction with other microbes, such as Lactobacillus and Pediococcus, in beer production.


Lactobacillus is a lactic acid bacteria commonly used in the production of sour beer. This microbe is also responsible for the sour taste in beer. Lactobacillus is found in the environment and can be isolated from various sources, such as fruits, vegetables, and milk products. One of the best sources of this microbe is in natural fruit purees, such as raspberries, cherries, and blueberries.

Lactobacillus is a rod-shaped bacterium typically 0.50 to 0.75 microns in length. This microbe is Gram-positive and doesn't produce spores. Lactobacillus is a facultatively anaerobic microbe, meaning it can grow in the presence or absence of oxygen. This microbe is typically found in beer at levels of 107 to 108 cells per mL. It's a perfect microbe for beer production because it can survive in the harsh beer environment and quickly produces lactic acid, a key component in sour beer.


Pediococcus is a genus of lactic acid bacteria also commonly used in brewing sour beers. These bacteria are Gram-positive, non-spore-forming, and cocci-shaped. Pediococcus also produces lactic acid, which gives the beer a sour flavor. Pediococcus is often combined with other microbes, such as Brettanomyces, to create a more complex flavor profile.

It's a preferred brewery microbiology option for beer production because it's easy to control and doesn't produce off-flavors. It's also ideal for sour brews that require a long aging time, as it's a relatively slow-growing microbe. This slow growth allows for a more gradual souring process, resulting in a smoother beer with lower pH. The drawback of Pediococcus is that it can sometimes produce beer spoilage organisms, such as yeasts and mold.


brewery microbiology

Acetobacter is a genus of bacteria known for its ability to turn ethanol into acetic acid. This process is called oxidation, and it's responsible for giving the beer its sour taste. Acetobacter is found in beer, wine, cider, and even kombucha. While most brewers strive to avoid oxidation, it's an important part of beer production.

While Acetobacter is necessary for producing beer, it's also one of the most dangerous bacteria in a brewery. If left unchecked, it can quickly turn a beer overly sour and make it undrinkable. That's why it's important to carefully monitor your beer for signs of oxidation. If you see any off-flavors in your beer, Acetobacter is likely to blame. 

To prevent oxidation, be sure to store your beer in a cool, dark place. You can also add sulfites to your beer, which will help prevent Acetobacter from growing. When it comes to understanding brewery microbiology,  it's important to know your beer inside and out. By understanding the role of each microbe, you can ensure that your beer is always of the highest quality.

Learn More About Craft Beers

If you're interested in learning more about beer production using fruit purees or your customized recipes, check out our other blog posts on beer brewing tips and beer fermentation. You can also find additional information on our website about types of fruit beers, beer tastings, and beer pairings. 

At Fierce Fruit, we love beer, and we're passionate about helping others learn more about producing craft beer so you can create your own unique brews. We bring you the widest range of fruit purees for beer, cider, and wine production, with over 50 different fruit purees to choose from. Shop now or contact us to learn more.

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