Eureka, today the results from the fermentation tests I did with two yeast strains I isolated from a Girardin Gueuze and a 3 Fonteinen Gueze. The isolation for the Girardin strains can be found here, and the one for the 3 Fonteinen is here. I included the microscopy pictures which I already posted in older posts to get you an idea what kind of yeast I used (Fig 1/2).
Both yeast strains have a different morphology than typical Saccharomyces cerevisiae. I therefore assumed that these two yeast strains are from a different family like Brettanomyces, Kloeckera, Pichia etc.
Since I do not own the fancy techniques for determining the kind of yeast I have here, I used a different approach. To test if these strains are for example Brettanomyces, I inoculated two starters with these two isolated strains and waited…
02/29/2012: The starters were made with dried malt extract (20 g to 200 mL) and sterilized in a pressure cooker for approximately 15 min. Then let the starters cool down and inoculated them with a colony of each strain.
03/04/2012: Four days after inoculation. See what happened:
There was a pellicle in the Girardin starter! And something similar in the 3 Fonteinen starter as well! Eureka! And the smell of the starters was just incredible. A lot of funky, sourness (no acetic acid) and cherry notes. Now I am pretty sure that these yeasts that I isolated from the dregs are a sort of souring bugs indeed. I assume that both strains are from the family of Brettanomyces.
03/09/2012: The pellicles are gone and there is a sediment in the starters.
02/24/2012: Tasting of the starters: Both starters smell just incredible. A lot of funk is going on. But no sourness detectable on the palate. I assume that both strains in the starter are indeed Brettanomyces. Both yeasts will ferment some sour beer in the future for sure.