Of course, I'll explain the experiment.
The point was to briefly examine what conditions that gives best growth of yeast and bacteria (E. coli
and P. fluorescens
). Variables were:
Glukose as carbon and energysource: G (0,5% yeastextract) and G5G (0,5% yeastextract and 5% glucose)
Temperature: 25 and 37 degrees C.
pH: pH 7 (G5G) and pH4 (G5G, 0,3% tartaric acid)
Oxygen: aerobic / anaerobic
we transferred a suspension of yeast and bacteria to testtubes containing:
- G5G and 0,3% tartaric acid
- G5G in anaerob bottle to be incubated at 25 C
- G5G in anaerob bottle to be incubated at 37 C
all was incubated for 4 days.
We use a simple scale from 0 - +++ to estimate content of yeast and bacteria. The culture before incubation was yeast (++) and bacteria (+++).
I don't have all the results now. What I do know is that while the testtube with G5G contained some yeast and some bacteria, the bottle with G5G and tartaric acid contained only yeast. And lots of it. We will finish the experiment next monday, and I will have some better results then.
The point here is that it seems like the yeast outcompeted the bacteria in the culture with added tartaric acid. This is probably not because the bacteria has intolerance to low pH, as E. coli
has both respiratory and fermentative metabolism. Also, it should not matter if it was aerob ar anaerob conditions, as of course yeast has fermentativ metabolism. It would be good though to try anaerob conditions with different pH, but as this is just a small part and time is very limited in the labs, I haven't had a chance to try. Maybe some other time.
It also needs some testing. As Ransom says, not much point if it only lasts for a few days. However, the yeast will most likely last as long as it gets nourishment. It might also be a good thing to kickstart bottles, especially when using glass diffusors (mine takes hours to build up enough pressure).
I'll post back with more conclusive results when I have them. Meanwhile I'd love more comments on this, as it might be a waste of time
(so, someone will probably say "go pressurized". Which is true. But not as much fun