Thursday, October 8, 2015

Microbe Overview: Yeast, Brett, Pedio, and Lacto

Earlier this year, the AHA requested some info on the various microbes involved in sour beer production for a post they were working on (Sour Microbes: Yeast and Bacteria Explained). I wrote up the summaries below for brewer's yeast, Brettanomyces, Lactobacillus, and Pediococcus to help them out. Nothing ground breaking, but since I had it already hopefully other people might benefit form the overview (without the ultra-nerdy details of chapter 4 of American Sour Beers)!

Brewer’s Yeast - Saccharomyces cerevisiae (ale yeast) and S. Pastorianus (lager yeast)
Type: Yeast - Order Saccharomycetales (Family: Saccharomycetaceae)

Fermentables: Primarily glucose, fructose, sucrose, maltose, and maltotriose (also mannose, galactose, and raffinose. Lager yeast also can ferment melibiose.)

Important products: Ethanol, carbon dioxide, esters, and phenols (POF+ strains – mostly Belgian and Hefeweizen)

Oxygen: Beneficial for growth

Ideal temperature: 45-95F (strain dependent)

Speed: Fast

IBU Tolerance: High

Overall: Brewer’s yeast protects the wort and sets the stage for a traditional slow-moving mixed-fermentation duo of Brett and Pedio.

Brett - Brettanomyces bruxellensis (aka B. lambicus)/B. anomalus (aka B. claussenii)
Type: Yeast - Order Saccharomycetales (Family: Pichiaceae)

Fermentables: Primarily the same as Saccharomyces, but in addition dextrins up to 9-glucose chains. Some strains (beta-glucosidase enzyme positive) are capable of fermenting lactose, cellobiose (wood sugar), and gylcosides (from hops, spices, and fruit – which releases aromatics)

Important products: Ethanol, carbon dioxide, esters (create and destroy), phenols (converts what brewer’s yeast leaves behind into funkier forms), and tetrahydropyridines (toasty to mousy)

Oxygen: Beneficial for growth, but leads to acetic acid production

Ideal temperature: 58-85F (strain dependent)

Speed: Slow

IBU Tolerance: High

Overall: Works well on its own with a large enough pitch, or in tandem with any of the other microbes listed. Brett doesn’t sour the beers you brew, it makes the sour beer you brew delicious. Can do some of its best work without malt carbohydrates available to ferment (especially during bottle conditioning). More fermentables allow the production of more esters, but these fruity flavors are not driving traditional funky “Brett” character.

Lacto - Lactobacillus delbrueckii/L. brevis/L. buchneri/L. plantarum etc.
Type: Bacteria – Family Lactobacillaceae

Fermentables: Some species can only ferment relatively simple sugars, while others can ferment dextrins.

Important products: Lactic acid, ethanol, and carbon dioxide

Oxygen: Usually aerotolerant (doesn’t use oxygen, but isn’t harmed by it)

Ideal temperature: 70-115F (strain dependent)

Speed: Really fast

IBU Tolerance: Low to very low

Overall: Lacto is capable of sour a beer within 24-48 hours if given free reign. However, too much acidity can cause less desirable performance for the microbes that follow. Most strains do not thrive after primary fermentation is complete.

Pedio - Pediococcus cerevisiae et al.
Type: Bacteria – Family Lactobacillaceae

Fermentables: Complex sugars, some species are even capable of metabolizing starch.

Important products: Lactic acid, exopolysaccharides (EPS), and diacetyl

Speed: Really slow

Oxygen: Usually microaerophilic (prefers oxygen at lower than atmospheric concentration)
Ideal temperature: 60-80F (strain dependent)

IBU Tolerance: Moderate

Overall: Pedio should be used with Brett in most cases to clean up the EPS and diacetyl. Won’t lower the pH as quickly as Lacto, but can reach a lower final pH given enough time and complex carbohydrates.


UltraSaha said...

Hi there! Chapter four is exactly where i'm now, and yes, its quite nerdy.
I got a question, i don't know if its the place to launch it, if not, let me know.
I would like to brew a dry hopped Berlinerweisse and my question is about PH.
I'm trying to do the system you made with the apricoc, as first prepare the wort, then put lactobacilus to work (hope its omega but difficult to get it in europe or WLP debruki) and then low temperature and ferment with WLP Kolsch. My question will be if you add sacharomices by tasting when wort is sour enough or if you are looking close de PH , which is the recomended range of PH for Saccharomices, in my particular case Kolsch.
Congrats for your blog and your book (hope to finish it soon).
Thanks in advance and apologies for the messy question.

Unknown said...

Weizen yeast is a completly different beast, isn't it?
As far as I know it's Torulaspora Delbrueckii.
Really cool summary! Thx
Ronaldo Dutra Ferreira

The Mad Fermentationist (Mike) said...

If you can get WLP L. brevis, that is a much better strain than the L. delbrueckii! It can be difficult to judge by flavor because the sweetness of the wort. It is best to aim for a target pH of 3.3-3.5. Much lower can cause fermentation issues for most Saccharomyces. Best of luck, and let me know how it turns out!

Ronaldo, that is certainly something I’ve read in a number of reputable sources, but here’s a post that lays out the case that the Weihenstephan isolate anyway, is S. cerevisiae. Opening Bruxa soon!?

Unknown said...

Everything's set. Equipment will arrive next week. Should be operational by 11.01. Hope to have you over to brew some beers soon! Say Hello to Audrey!

Rob Miller said...


Thanks for the overview of these funky friends. You forgot one: Acetobacter. It works very fast. I got it accidentally when I was making a light version of a sahti. Since I was already planning to drink it young, it worked out beautifully. I think most folks are scared of the aggressive nature of aceto, but I think it works very well in certain unhopped beers.
Cheers, and thanks again for all the work you put into this blog.

Unknown said...

Any chance of adding pH tolerances?

The Mad Fermentationist (Mike) said...

I do everything in my power to limit Acetobacter. I did include a section about it in the book (as well as a few other more positive contributors). Certainly in a case like yours it can work, although likely not for my tastes.

It seems that pH tolerance (and ABV tolerance) is pretty strain specific. Sadly not something that is conducive for this high-level overview.

Unknown said...

My parents live near DC and last time I was there we went to bluejacket and it completely floored me. I had never been to a brewery where every single beer was basically what is the most intersting and unique beer at any brewery. Food was spectacular too.

I also made it to Ocelot, but this was before they officially opened. Only had 3 beers to offer but it was very cool. Liked the barrel vibe of everything in the taproom. Im wondering if they ended up having to secure down those seats which are just planks resting on top of barrels

Cyber Raven said...

I've been reading through your sour write ups (fantastic, thank you so much for the comprehensive coverage of the subject!) and lusting over ideas that I can't actually execute. There's no way I can fit several retired wine barrels in my Arlington townhouse.

Is there any place in the area that's doing decent sours right now? Aside from the usual geuzes and the limited release Anderson Valley did, I haven't been able to lay hands on much of anything.

The Mad Fermentationist (Mike) said...

BlueJacket and especially Right Proper do some nice sours. A few other local places dabble, but I have yet to have anything else I've loved.

UltraSaha said...

Hi there! Finally i made the dry hopped berlinerwiesse, using Omega lactobacillus (thanks to a friends travelling to Chicago) and a simple grain list: just pils malt 60%, and wheat malt 60%. Collected near 35 liters or wort and heated them to 85º celsius. Let naturaly drop temperature to 40ºC. First problem: move such a heavy kettle to the freezer where i have te temperature control (brewpi)...Added 1 liter of lactobacillus starter (24h, no stir plate) and in 32h took the first PH measure... 3.1, Little worried about maybe too much acidity i boiled (15 minutes added 8 IBU of Saaz), cooled as usuall and added 1.5 liter of WLP029 Kolsch. In 8 hours signs of strong fermentation. Let it for a week, and reached 1.010, added 100g of Nelson Sauvin and 50g of amarillo. Bottled with 6g/l dextrose. It has tourned a beer with a great aroma of white winne and some peach and a good level of acidity. My friends are asking to brew again in summer. Thanks for the tips Mike!

The Mad Fermentationist (Mike) said...

Sounds delicious, glad it worked out well for you! If you ever do overshoot the pH drop, you can always dilute with some fresh wort.