I am culturing Haematococcus in 20L carboys in BBM with air bubbling and observing a layer of foam building up on top. I have inspected microscopically and it looks fine. Why do we see foaming in microalgal cultures?
One possible explanation is 'broken or lysed cells'. Proteins and membranes lipids released from cells are good stabilizers for foam. Perhaps you are bubbling at a too high rate (shear stress) or the cultivation conditions are suboptimal (too high light, wrong salinity, carbon/nutrient shortage, extreme temperature,...).
Another option could be excretion of EPS (also can stabilize foam), although I'm not aware of haematococcus excreting much of that (but I also have only little experience with this species).
Best regards,
Packo
I would check your pH. I tend to see increased foaming in cultures bubbled with air and no added CO2.
Cell lysis is the most logical answer, especially if this is seen in late stationary phase.
Thanks all!
I did see some broken and empty cells in the culture so I agree its the cell lysis. I am not giving CO2 but to get high biomass, I would give CO2.
Delighted to get answer from Prof Cooksey.
There are several reasons for foaming to occur in microbial cultures. First check the level of nitrogenous substances you have added to the medium like proteins or proteinic hydrolysates, check if you have any surface tension reducing agents being added to the culture. However, when the microorganisms grow, they do partially hydrolyse the proteins which produce foams. like these there are several reasons for foaming to occur. Note that aeration and agitation enhances foaming too.
Foam might result from decaying cells, but also from compounds secreted from cells when entering the stationäre phase, See e.g. Phaeocystis globosa.
A simple experiment: ad some dead cells to a not foaming culture....
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