Lactic Yeast Throwdown

Over the past couple of months I’ve been doing a deep dive into the biology and fermentation characteristics of two lactic acid producing yeast (hereafter called “lactic yeasts”). The first of these, Philly Sour, is a strain of Lachancea thermotolerans isolated in Philadelphia. While it is a bit harder to work with than conventional brewing yeast, it is an interesting strain that is useable in the brewery (Post 1 | Post 2). The second is Sourvisiae, a genetically modified yeast. Both strains are notable for producing lactic acid, allowing for single-organism quick sours. But they are otherwise quite different from each other.

In this post I am doing a split-fermentation batch of beer, fermenting half with Philly Sour, and the other half with Sourvisiae. This is a variation on a quick sour that I brew once or twice a year, but because I’m not using Lactobacillus in this beer, I’m moving half the dryhop charge to a whirlpool addition.

Caveat Emptor

Below you will see that I have a clear preference. I want to state up-front that this preference is specific to this recipe and should not be taken as an “x is good, y is bad” type of conclusion. These are very different yeasts, and each has recipes in which they will shine, and recipes in which they will not.

Lactic Yeast Throwdown – Recipe & Brewing


2.50 kgPilsner Malt43 %
2.70 kgWheat Malt47 %
0.45 kgFlaked Oats7.9 %
0.10 kgRice Hulls1.7 %
28 gMosaic (12.25 %), 20 min whirlpool10.3 IBU
28 gMotueka (7.00 %), 20 min whirlpool5.9 IBU
28 gMosaic (12.25 %), 3 day dryhop
28 gMotueka (7.00 %), 3 day dryhop

Water was adjusted to have 120 PPM Chloride, with a sulfate:chloride ratio of ~1:3. Grain was mashed at 65.2 C (~149F) for 60 minutes and then sparged to collect ~27L of wort.

The wort was brought to a boil, and the heat immediately killed. Once the kettle had cooled to 90C (195F), 28 g (~1 oz) each of Mosaic and Motueka were added and whirlpooled for 20 minutes. The beer was then chilled, split into two 12-liter fermenters, and starters of Philly Sour and Sourvisiae pitched.

Philly Sour was pitched at a rate of 1 million per mL, which my previous work showed was an ideal rate for this yeast. Sourvisiae was pitched at a rate of 2 million per mL, which my work also shows is a good pitch rate.


Both beers were fermented at 20C (68F), which was a compromise between the best temperature for Philly Sour and Sourvisiae. Visible fermentation was complete with Sourvisiae after 5 days, and after 8 days for Philly Sour. Dry hops were added on day 10, 28 g (1 oz) each Citra, Mosaic and Motueka split evenly between the two beers. At this time I also allowed the beers to cool to cellar temperature (~14C). Three days later I kegged the beers.

Tasting Notes – Lactic Yeast Throwdown IPA

StatisticSourvisiaePhilly Sour
ABV5.8 %6.2 %
Terminal pH3.213.64
photo of two IPAs fermented with lactic yeast,
Lactic Yeast Showdown Beers. Left: Beer fermented with Sourvisiae. Right: Beer fermented with Philly Sour.
SourvisiaePhilly Sour
AppearanceGolden in colour, slightly hazy. Pours with a thick and luscious head that lasts forever and leaves stands of Belgian lace on the glass.Golden in colour, moderately hazy, pours with a courser and shorter-lived head than the Sourvisiae version.
AromaIntense citrus/lemon and “generic tropical fruit” aroma. The high acidity of the beer is also apparent in the smell, as a sharp sensation in the nares.A mild papaya/blueberry note with an unusual soap-like note in the background.
FlavourThe hops leap from the glass, grab your tongue, and don’t let go. The hop character has a wonderful lemon/citrus note that is bold and up-front. Behind this is a tropical fruit hop character – mostly mango, but with a hint of an almost pineapple-like note. As the citrus and tropical flavours fade a final papaya and berry note appears. Some hop bitterness is apparent, mostly in the aftertaste, and is well balanced with the hop notes. Very little malt character is to be found, although a slight breadiness appears as the hop note fades. These intense hop notes are accompanied by a bold acidity. For my palate the acidity is bordering on too much – and I love acid bombs! I’d describe the acid level as closer to the acidity I would expect in an old lambic or gueze. It is a touch more acid than I would normally shoot for in a dry-hopped sour, and is well above what is typical in commercial examples of this style.Despite being the exact same beer as the sourvisiae version, this tastes completely different. Up-front, the vibrant hop flavour of the sourvisiae version is completely absent, and is replaced by more muted hop notes. The “presentation” of the hops is also completely different, with the citrus notes deemphasized and in the aftertaste. The papaya character that was almost invisible in the sourvisiae version is, in this beer, the dominant hop character. The hop bitterness is also much more apparent in this version, and borders on a “biting” intensity. Unlike the sourvisiae version, which lacked any notable yeast character, a very unique yeast flavour dominates this beer – both in the up-front flavour and in the aftertaste. This flavour is hard to describe, but is slightly medicinal and herbal, and even a touch “soapy”. This yeast note, along with a lingering bitterness, dominates the aftertaste.
MouthfeelThis is a very crisp and dry beer, amplified by an intense acidity. Extremely refreshing, but acidic enough that its hard to drink more than one glass at a time.This beer sits heavier on the palate than the sourvisiae version, and also lacks the crisp, dry character. The mouthfeel is fuller, and the beer “feels” sweeter. I wonder if this yeast produces some glycerol, as this could account for that mouthfeel and sweetness.
OverallThis is an amazing beer with one flaw – it is too acidic, at times boarding on giving you heartburn. But the yeast amplified and highlighted the hop aroma, making this a wonderful hop bomb. In the future I would rebrew the same recipe, but add in ~10% (by cell number) US-05 or another chico strain to help cut the acidity. Another interesting option would be to blend a split-batch of beer, half fermented with Sourvisiae and half with a fruity kveik, to really amp-up the hop and fruit notes.Also an amazing beer, but given the recipe, a bit of a disappointment. The relatively muted hop character is not what I was looking for with this recipe, while the yeast note detracts from what hop character is present. That said, the flavours made by this yeast are intriguing and very much have a place in the brewhouse. I could see brewing a beer more along the lines of an APA, where the yeast character is the feature, and the beer is lightly dry hopped with a hop like Simcoe, where the dank and herbal/oniony flavour would accompany the yeast character. It would also be great blended into a saison or other farmhouse-style ale.

Lactic Yeast Throwdown – Overall

Clearly, these two yeast are very different in their fermentation characteristics. For the style of beer brewed in this post, Sourvisiae is the clear (if somewhat overly acidic) winner. But that is not to say that Philly Sour is a bad yeast, only that it’s better used in other styles of beers – or, perhaps – with a different hop bill. Sourvisiae produces a very clear, acidic beer. As such, it’s place is in recipes where you need the yeast to “get out of the way” to let other ingredients shine through. Philly sour has a distinct and interesting yeast character that would work in many styles, and which could easily be a “feature flavour” in a beer.

I have been drinking these beers mostly as an 80:20 blend of Sourvisiae:Philly Sour. This keeps the bold hop character of the former, while bringing in a touch of complexity and lower acidity from the latter. But it remains a less-than-ideal blend, as the “soap” and hop-dampening character of the Philly Sour is apparent even in this diluted state.

6 thoughts on “Lactic Yeast Throwdown

  • January 15, 2023 at 3:10 PM

    Would you consider raising the mash temp to retain some non fermentables a way to slow down acid production with sourvisiea?

    • January 17, 2023 at 9:30 AM

      That should work, but I’ve not tested it myself.

  • January 3, 2023 at 12:18 AM

    Thanks Bryan. Lallemond puts out good literature on these yeasts, but it is no substitute for the profound knowledge gained from brewing and tasting. I appreciate you sharing this with us. Second hand gold is as good as new.

  • March 20, 2021 at 6:18 AM

    I see where folks co-pitch US05 or Wyeast 1007 along with the Sourvisiae to mellow out acidity. Might be an interesting experiment..add lactic bug before, with , after clean yeast.

    • March 20, 2021 at 10:13 AM

      That’s my plan the next time I use it – or perhaps a saison/sourvisiae blend.


Leave a Reply

Your email address will not be published. Required fields are marked *