The topic of using probiotic Lactobacillus (and other cultures) for producing kettle soured beers comes up often in the sour-brewing world. Often, brewers reach for a probiotic food or supplement, not because they want a probiotic beer, but rather out of convenience. But is there an added advantage of using a probiotic strain in place of a non-probiotic strain? Are there downsides? And is the beer itself probiotic afterwards?
I’ve written previously on how to select a probiotic for wort souring, so this article is going to focus more on the health-related aspects of using probiotics for souring wort.
What is a Probiotic Anyways?
Before we get into the details, its worth briefly touching on what a probiotic is – and isn’t. Probiotics have a very strict scientific definition, which in most countries, is also the legal definition: A live microorganism which, when used in adequate amounts, confers a health benefit to the host. That definition has a number of implications, but there are a few key points that come from it:
- Most species are not probiotic.
- Even if a species has a probiotic member/strain, most strains within that species will not be probiotic.
- A particular strain of microorganism is only probiotic if it has a measurable health benefit.
- If a food/supplement contains a probiotic strain, but at too low a dose to be effective, is not a probiotic food/supplement.
- Because a specific health benefit (e.g. efficacy against a specific disease or condition) has to be demonstrated for a strain to be classified as a probiotic, the practical utility of probiotics is limited to specific diseases or disorders – i.e. claims of general health benefits are not supported.
By extension, most of the claims you see in the marketing of probiotic foods and supplements are – to be polite about it – utter bull shit. Putting a microorganism in your yoghurt which helps to prevent antibiotic-associated diarrhea, for example (I’m looking at you, goodbelly), doesn’t do you a lick of good…unless you have antibiotic-associated diarrhea. In other words, in many cases, probiotic-containing foods/supplements are a marketing gimmick without measurable benefit to your health.
They are good for inducing weight-loss in your wallet, however!
But I digress. There are a number of biological features that can give a strain probiotic properties. It’s too much to review here, but in simple terms:
- Some probiotics produce metabolites which alter immune cell activity (usually in an anti-inflammatory fashion). These can reduce symptoms of inflammatory diseases such as irritable bowl disorder.
- Some probiotics produce bacteriocins – antibiotic-like chemicals which allow them to compete with non-beneficial microorganisms.
- Some probiotics can adhere to the gut wall, preventing more damaging organisms from doing so.
Its also worth mentioning that probiotics can and do cause harm – they are live microorganisms after all. Probiotic organisms can cause life-threatening infections. And using the wrong probiotic at the wrong time can also cause issues. For example, giving young children the wrong probiotic can increase their risk of developing allergy later in life, and giving someone with pancreatitis a probiotic is downright lethal.
Why Aren’t All Strains of the Same Species Probiotic?
The answer here is simple – for the same reason that not all people have brown hair – genetics. Probiotic activities require specific genes, and these genes tend to be relatively rare.
To make matters worse, these genes are often on plasmids – small circular arrays of a few genes that are distinct genetic elements from the bacterium’s main genome. Plasmids can readily be lost if the genes on them are not needed, meaning that without careful culture these genetic features can be lost. Sadly, many manufacturers of probiotic goods don’t culture their bacteria properly, and if you analyze the genetics of their products, they lack the probiotic genes that you are paying a premium for.
I’ve included an example of this loss of probioitc activity in the image to the left. This is an experiment from the course I teach, where we plate spots of probiotic organisms that produce bacteriocins – antibiotic-like chemicals used to kill competitors. At the top of the plate you can see two strains which kill the neighbouring pathogen, producing cleared areas. At the bottom are the same two strains after being mis-cultured. The strains up-top are probiotcs used to prevent caries (tooth cavities); the bottom strains are no longer probiotic.
I Thought we Were Talking About Brewing!
Time to get back on-track. The take-home message from everything I wrote above was intended to be simple – most bacteria aren’t probiotic, and even those which are, are unlikely to benefit your outside of a limited set of clinical conditions and dosing ranges. So it isn’t really useful to spend extra for them – for use in the brewhouse in particular. That said, high-dose probiotics are often available at prices far lower than an equivalent cell count of a strain packaged for brewing. So a cost-savings can be had in some cases.
But the other thing to take from what I wrote about is that probiotic strains are minimally different from non-probiotic strains of the same species. So while they may not offer anything special for your brewhouse, probiotics can (generally) be substituted for “brewing specific” strains without consequence…but with exceptions.
When is Substitution Fine?
The answer here is “almost all kettle/quick sours” at least so long as you are referring to Lactobacillus. The main things we want from Lactobacillus in the quick-sour brewery is the production of lactic acid with minimal/no off-flavour production. From a brewing perspective, this means we want strains of Lactobacillus with two characteristics:
- An ability to metabolise the sugars present in wort (e.g. sucrose, fructose, glucose, and maltose), and
- Sugar metabolism that doesn’t produce significant amounts of off-flavours that cannot be later cleared up by yeast (e.g. butyric acid)
With only a few exceptions, most Lactobacillus species will meet those criteria. A rare few (L. kukuneii) lack the ability to ferment many of those sugars, and some can produce unwanted off-flavours such as acetic acid (e.g. L. parabuchneri) under some circumstances. Luckily, none of these species are used as probiotics – and indeed – are rarely encountered outside of beehives (kikuneii) or contaminated dairy products (parabuchneri).
It is worth noting that all Lactobacillus species can produce significant amounts of acetaldehyde, butyric acid, and diacetyl under the right conditions. Luckily for brewers, Lactobacilli make these compounds primarily when metabolizing fat. So you rarely see these produced in beer – while the exact same strain used in cheese or yoghurt production will produce these chemicals abundantly. The presence of these compounds in sour beer is most often a result of contaminating bacteria or yeasts, not from Lactobacillus.
So in many cases – kettle souring in particular – you can substitute in one species/strain of Lactobacillus for another without consequence – probiotic strains or otherwise.
When is Substitution Problematic?
There are some conditions where choosing a random probiotic (or non-probiotic) strain may not be a good idea. The most prominent of these is if you are building a mixed culture intended for a more traditional-style mixed fermentation. Most probiotic Lactobacillus strains lack any tolerance to hops, meaning that they are unlikely to do the desired job in a mixed culture pitched into hopped wort.
Another reason to avoid using probiotic strains in a mixed-culture situation arises if you are using more than one species of bacteria (e.g. if adding both Lactobacillus and Pediococcus). If you accidentally select a bacteriocin producing probiotic it is possible that it will kill off the pedio. Many of the bacteriocins produced by Lactobacillus target closely related species, and some strains of Lactobacillus have been shown to target Pediococcus with bacteriocins. This isn’t a 1-way relationship, as some Pediococcus strains produce baceriocins that target Lactobacillus.
As such, if you are intending to use Lactobacillus either in a hoped wort, or in a mixed culture, it is best to use either a commercial Lactobacillus brevis strain* with established hop tolerance, or use a wild isolate of your own that has grown successfully (and recently) in hopped wort. These should be hop-tolerant and compatible with the presence of brewing strains of Pediococcus.
*many yeast companies are producing cultures of Lactobacillus planetarium. This species is not normally found in beer and lacks any notable hop tolerance. Therefore, it is not suitable for use in mixed cultures or for souring hopped wort ***even though available from yeast manufacturers***.
Of course, Lactobacillus is not the only organism found in probiotics, and you may be tempted to use a product that contains organisms other than Lactobacillus. Some of these (e.g. Bifidiobacter) are highly sensitive to oxygen and will die pretty quickly after being added to wort. Others, though, can be problematic. There are some Clostridium and Escherichia used as probiotics, largely because they can produce large amount of inflammation-dampening propanoic and butyric acid. These are off-flavours (body odor and rotten butter, respectively) that you do not want in beer.
Another organism found in some probiotics is Saccharomyces cerevisiae var. boulardii. While technically of the same species as ale yeast, this strain of yeast is notorious for having difficulty fermenting wort to completion and of flocculating out of the beer. Reviews of the flavour of this yeast have been mixed, with most people (myself included) finding its flavour profile to be unpleasant, but a few reporting hefeweizen-like and witbier-like character. If you find one of the later strains, than it may be a good choice, but care needs to be taken.
OK, But Is My Beer Probiotic?
One reason you may want to use a probiotic strain is to make a probiotic beer. But will you? The answer is “probably not”. Keep in mind that to be probiotic, a product needs to be produced with a probiotic strain, and that strain needs to be present – alive – at sufficient numbers in the finished beer.
The later issue is the one which makes probiotic beer a near-impossibility. Most clinical trials of probiotic organisms find that you need to provide patients with at least 1 x 10^11 (AKA 100 billion, as in 100,000,000,000) live cells of probiotic *per day* to achieve a clinically measurable effect. Kettle sour beers peak at 10^8 (100 million) to 10^9 (1 billion) cells per ml, with that number dropping off rapidly after fermentation. Co-fermented sours peak at levels 100 times lower than quick sours. At kegging, my last kettle sour had 2 x 10^6 (2 million) Lactobacillus plantarum per ml based on a hemocytometer count. Mixed fermentations such as Lambic, post-packaging, typically have under 1 million Lactobacilli per ml.
What this means is that you would need to drink, to get a single probiotic dose (10^11 cells), the following amounts *per day*:
- 100 ml to 1 L of kettle-soured wort (before yeast addition). That’s equivalent to 1/3rd to 3 standard beers.
- 50 L to 200 L (150 to 600 standard beers) of quick-soured beer, freshly packaged.
- 1,000 L or more of a traditional mixed fermentation beer, freshly packaged.
In other words, once the Saccharomyces is done turning your wort into beer, you’d have to give yourself acute alcohol poisoning to get a probiotic dose of Lactobacillus. And that’s assuming that 100% of the Lactobacillus is still alive (it won’t be) and that it didn’t loose its probiotic genes during beer production. Depending on the strain, the likelihood of losing the probiotic genes could be as low as 0%, or as high as >99%.
The take-home here is simple: probiotic strains of Lactobacillus can generally be used for kettle souring approaches, so long as you are souring an unhopped beer. They should be avoided for hopped worts and mixed-fermentation approaches (with the exception of pre-souring a beer before pitching a mixed culture).
But while they can be used for quick souring, they will not make your beer probiotic. And even if they did, the known risks and dangers of alcohol consumption would far exceed any marginal benefit they would provide.