Dear community,
He have observed several times in our reactors a contamination by an unknown filamentous algae.
It forms greens patches of biofilm at first, which grows to form green/brownish thick biofilm with time. Under the microscope (see pictures), it appears like thin pale green filaments, rarely in suspension (concentrated in biofilm however).
We cultivate our spirulina in Zarrouk medium, and this contaminant is a huge problem for us.
We think it may be Phormidium sp.
Do you have any hint on its nature, and how to get rid of it ? (or at least control it)
The best way is physical removal to start an unialgal culture.
Fully optimize the growth rate of Spirulina by altering the relevant growth parameters. Once the growth of Spirulina has gone to a higher level, then such a condition would snuff off presence of others in the system.
Thank you for your answers.
We still have clean inocula to restart our experiments, but as our cultivation system cannot ensure an axenic cultivation, we are looking for a way to control the contamination level and avoid to discard the whole culture in case of contamination.
We have begun to try altering some cultivation parameters, but without success for the moment... increasing NaCl up to 5 g/L or adding 50 mg/L urea seems uneffective, maybe we did not reach threshold concentrations or are working on the wrong parameter...
Alas, without a more precise knowledge of this contaminant, we are sailing in the fog...
Dear Ivan, what is your culture pH? I'm asking this because the Zarrouk medium by itself has a low pH. you have to raise it by adding some NaCO3 (8 g/l) to reach the pH about 9.5 and after spirulina get dense enough (normally after one week) it will be reach to 10.5 by itself.
It turned out it is a Phormidium sp., identified with the help of spirulina producers.
It has the following properties :
- Grows in the same conditions as Arthrospira platensis
- More resistant to low and high pH, low and high salinity, low and high temperature than A. platensis
- Grows in biofilms -> not a critical problem in raceways
- Benthic -> almost absent in dark zones.
- Very invasive -> a single filament is enough to contaminate. Just start from frash cultures.
Hi Ivan Feurgard : I have same problem. Did you solve it?
Hi Ahmad Nosratimovafagh , can I increase PH by increase NaHCO3?
Anh Nguyen: although the NaHCO3 is a good buffer it can not raise the pH. In fact, when algae use It as a carbon source It can turn into NaCO3 and raise the pH but in low density, there isn't enough biomass. For increasing the start pH, the best option is NaCO3. If you don't have access to NACO3 don't be worry! you can heat NaHCO3 in the oven at 200 C for 2h or simply put the NaHCO3 in a pan and heat it until the color turns whiter and the particles pop up.
Ivan Feurgard Ahmad Nosratimovafagh Anh Nguyen
So, the conclusion of Phormidium sp., It's need to be eliminate or not ?, I'm so confused @_@
Some of the spiral filaments can be converted to linear filaments at stress conditions. First be sure that it has not happened.
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