I have only used 'natural' lactobacillus, that is, inoculated wort with raw grains to achieve a very tart sour. In my last experiment, I soured a mash over a few days and the gravity had dropped from 1.042 to 1.008 without ever having added yeast. I ended up just adding yeast, since I was hoping to retain some of the alcohol content (rather than boiling first to stop the lactic acid production). In the end it was more of a lacto-lemonade, as it had a great sour taste, but little to no alcohol (1.008 -> 1.004, plus whatever was there from the sour). I couldn't think of any other way to "test", so I just downed two pints, but to no effect :-) In doing some reading here, I discovered some lactobacillus actually does create alcohol, but I suspect this is not true of the brewers' type, as Wyeast doesn't mention any attenuation. However, White Labs, here and here do mention attenuation, so perhaps the white labs strains are heterofermentative? Or perhaps they are simply referring to the apparent attenuation of the sugars (as the lacto definitely eats through them)?


Don't know if there are other species used in homebrew, actually I've never gone that way before, but the two species that you cited above, Lactobacillus delbruekii and Lactobacillus brevis are homofermentative and heterofermentative respectively according to this text of Todar's Online Textbook of Bacteriology (page 3):

Lactobacillus is very heterogeneous genus, encompassing species with a large variety of phenotypic, biochemical, and physiological properties. Most species of lactobacilli are homofermentative, but some are heterofermentative. The genus has been divided into three major subgroups and over 70 species are recognized. Group I lactobacilli are obligately homofermentative and produce lactic acid as a major end product (>85%) from glucose. They are represented by L. delbrueckii and L. acidophilus. They grow at 45oC but not at 15oC. Group II, also homofermentative, grow at 15oC and show variable growth at 45oC. Represented by L. casei and L. plantarum, they can produce more oxidized fermentations (e.g. acetate) if O2 is present. Group III lactobacilli are heterofermentative. They produce lactic acid from glucose, along with CO2 and ethanol. Aldolase is absent and phosphoketolase is present. Representative species include L. fermentum, L. brevis and L. keferi.

Michael Tonsmeire (The Mad Fermentionist) in an article about a batch of a 100% Lactobacillus Berliner Weisse, says that Wyeast 5335 "is only capable of fermenting about 10-12% of the carbohydrates in a standard wort, not nearly enough attenuation for something resembling beer", and that White Labs WLP677 (L. delbrueckii) "produces both alcohol and carbon-dioxide, so the result should be similar to a beer fermented with yeast".

Brew Your Own magazine, in an article about sour mash, says that "L. delbruckii is homofermentative, thermophilic and anaerobic. Homofermentative means that L. delbruckii produces only a single product — lactic acid — when they ferment."

According to the first and last texts, it seems that L. delbrueckii would not be able to produce alcohol while Tonsmeire suggests that is possible. Maybe its just a 'strain number' problem. Read his article, it has a ton of comments that may help you.

  • 1
    Nice ;-) Thanks for the great information. You are right, TMF mentions in a comment that some delb* is and some isn't, and that white labs IS, but in his taste tests, it appears the lactic acid was minimal. This is very helpful in understanding the process. I think in the future, I will use the same method, but have my yeast ready before souring, and immediately boil the wort when it is sour to taste, adjusting with DME if needed to bump the SG back up before fermentation. I think it's the only way to really control it.
    – Wyrmwood
    Sep 22 '14 at 22:09
  • 1
    Cool, man, I really enjoyed doing this research! Good luck!
    – jards
    Sep 23 '14 at 16:18

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