Lacto Brevis vs. Delbruekii

[lshaner]

There is increasing evidence from this post and elsewhere (see milk the funk wiki) that some commercial pitches of lacto have sac and/or other organisms present. This would certainly explain some of the reported behavior of the strains in this post by myself and others. Even very small amounts of other organisms - perhaps not easily detectable under a microscope - could have the ability to reproduce, especially under conditions such as those i used (high temp/lots of food).

to test this hypothesis is not trivial, at least i cannot think of a very good way, but i am not a microbiologist. Perhaps someone can weigh in on this? My initial thought is to take several samples from the pitch in a sterile environment after sanitizing packaging and then again after the same samples post fermentation.

Any suggestions would be appreciated.

Regardless of the outcome, both these strains produce tasty beer and i highly recommend them as a way to quickly produce acidity (at least in the absence of hops).

Post-fermentation is very easy to test if you have access to or know someone with access to a microscope. If you have krausen development or see a lot of CO2 off-gassing, yeast will be easily visible under the microscope.

Even if a commercial container is infected with yeast, it may or may not be visible under the microscope (though more often than not, I have been able to see yeast under the scope straight from the container). The more sure-fire way to test directly from the commercial package would be to plate a 0.5-1 mL sample on a nutrient agar plate containing an antibiotic such as ampicillin. This will kill the bacteria but allow yeast to grow.

 

[dantheman13]

There have been multiple reports of finding yeast in WL bacteria vials when looked at under a microscope on MTF. I'd say we've seen these reports now for about a year or so, and it seems to offer a good explanation for what would otherwise seem to be biologically impossible. Lance Shaner and others have done a lot to show that this is the case. Additionally, WLP677 is "delbruekii", which is not a heterofermentative species. It is either mislabeled, or WL is incorrect about it being heterofermentative. Regardless of that, as Lance has said, Lacto does not produce a yeast-like fermentation. We recently had Kara Taylor comment on the issue as well in MTF, and she said that once they move to the new PurePitch tech for bacteria, the issue should be solved (she said the problem is on their packaging line).

As has been mentioned in this thread, most Lactobacillus scientific studies have not been in a wort/beer environment. Most of it is in cheese or other fermented products, or biotech type stuff. More recently, however, a group of researchers from Belgium looked at flavor development of Lactobacillus in wort fermented beverages. In a presentation, one of the researchers (an expert in Lactobacillus) noted that "Lactobacillus did not ferment more than 0.5°P regardless of starting gravity". When asked why at the end of the presentation, the researcher said she did not know for sure, but suspected that Lactobacillus inhibited themselves and did not need much sugar in order to max out their growth. See this section on the MTF wiki, along with the video: http://www.milkthefunk.com/wiki/Lactobacillus#100.25_Lactobacillus_Fermentation

 

[bigdee4933]

Brevis straight from the package.

 

[Hommel]

can you change the focus? those rod shaped small things are hard to see behind those larger round things.

 

[Agate]

can you change the focus? those rod shaped small things are hard to see behind those larger round things.

I'm sorry, but THAT was funny!