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Beer Science: Lactobacillus in Beer

Last weekend I was visiting friends when a bottle of Off Color Brewing’s Troublesome unexpectedly was poured into my glass.  A few minutes later, we also tried another beer: Ithaca Brewing Company’s Cayuga Cruiser.  Not being incredibly familiar with either of these beers, I was essentially conducting a blind taste test.  Below is a picture of the two beers that were tasted:

Ithaca Brewing Co.: Cayuga Cruiser, a Berliner Weissbeer
Off Color Brewing: Troublesome, a Gose

Little did I realize, but these two beers actually had a very important similarity.  Both of these sour tasting beers were made with a bacteria called Lactobacillus (frequently shortened to “Lacto”).  Most beer is made with a fungus called Saccharomyces, more commonly known as yeast.  So why would anyone make a beer with a Lactobacillus bacteria?

Lactobacillus Is a Normal Bacteria Found in Humans

There are about 180 species of Lactobacillus that have been identified.  These species exhibit a wide range in terms of health and commercial effects.  Lactobacillus exists as a normal bacteria and is found in numerous locations on the human body including the mouth, stomach, intestinal tract, and vagina.  These bacteria actually are considered “good” because they fend off other “bad” bacteria invaders by competing for space and resources in your body.  In fact, research on Lactobacillus suggests that these bacteria can be beneficial when taken as a probiotic.  Lactobacillus is believed to useful for treatment of diarrhea in children, abate milk allergies, and help reduce the effects of certain respiratory infections.  Below is a picture of Lactobacillus taken from the inner lining of cells in the human vagina.

Lactobacillus can seen as small purple rods inside a much larger pink colored vaginal epithelium cell.

Like Yeast, Lactobacillus Ferments Sugar

From a microbiology point of view, Lactobacillus carries out a similar metabolic pathway as Saccaromyces, commonly known as yeast.  As the chart below indicates, Saccharomyces is of widespread importance in the production of wine and beer.  Lactobacillus is important in production of cheddar cheese, yogurt, and soy sauce.  Lactobacillus is used to acidify food and produces a “sour” flavor.

Lactobacillus casei
Lactobacillus casei is used in yogurts and fermented milk.

Lactobacillus, yeast, and other organisms found on the chart below all carry out fermentation.  Fermentation is a metabolic process that converts sugars to acids, gases, or alcohol in the absence of oxygen.  All organisms on the chart use glucose (sugar) for generation of energy.  But each group of organisms produces quite different products from their use of sugar.  Propionibacterium produce carbon dioxide and propionic acid.  Lactobacillus metabolize sugar and produce lactic acid.  Saccharomyces (yeast) produce carbon dioxide and ethanol.  And Clostridium produce acetone and isopropanol as a by-product of sugar metabolism.

Fermentation products
Organisms that ferment sugar produce a variety of chemicals, and are widely used in a variety of industrial products.

Lactobacillus in Beer Production

Lactobacillus are used industrially in the production of pickles, sauerkraut, pickers, and yogurt.  But hearing the word “Lacto” mentioned in a brewery is often met with consternation.  Lactobacillus can indicate that an unwanted infection has taken hold in the brewery.  And yet sometimes brewers invite this bacteria into a secluded corner of the brewery willingly.  But why?

For most beer styles, Lactobacillus is simply undesirable.  But for other styles, Lactobacillus supplies a pleasant and desired sour taste.  Styles including Belgian sour beers such as lambic, American sour beers, traditional Berliner weisse, Flanders, gose, and Belgian witbier all make use of Lactobacillus during fermentation and contain higher levels of lactic acid that other beer styles.  Many feel that this sour taste helps bridge the gap between wine and beer drinkers.  Historically, the origins of Lactobacillus use in beer production is quite ambiguous, and most likely a result of inadequate or improper sanitation methods.

Lactic acid, the byproduct of Lactobacillus fermentation.

All malt is actually covered in Lactobacillus bacteria, although most of the bacteria do not survive the boiling process during brewing.  Interestingly, Lactobacillus are one of the only non-yeast organisms that can withstand the biocidal effects of hops.  That is, hops will inhibit growth of most spoilage bacteria, but certain strains of Lactobacillus can survive.  Lactobacillus delbrueckii (named after Max Delbruck, a German chemist), is one such strain commonly used in the creation of sour beers.

Most breweries do either a split or subsequent fermentation.  In split fermentation, brewers can use Saccharomyces to ferment one batch, and Lactobacillus to ferment a different batch.  Later, these two separate batches can be mixed in a desired ratio to create a new sour beer.  Or, beer can be fermented first with Saccharomyces, and then subsequently fermented with Lactobacillus .  Beers that have Lactobacillus added possess sourness levels that range from barely noticeable to incredibly sour depending on the parameters used to construct each beer.

Sour beers are certainly gaining popularity as the craft beer wave sweeps across the nation.  There is a good chance you may soon taste a beer that has been produced using Lactobacillus bacteria.


References: Microbiology textbook, Bauman.  4th edition.
Oxford Companion to Beer.Lactobacillus casei picture.


About Buffalo Beer Biochemist

Born and raised in Western New York. Ph.D. in Biochemistry. Professor of Microbiology and Chemistry. And lover of beer.

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