We are attempting to cultivate unicellular cyanobacteria (Aphanothece, Synechococcus) in an open thin-layer cascade system (200 L, 18 m2). The system is in a greenhouse an we have years of experience with green algae. A first test with Synechococus in 2020 worked. Now, a year later, it doesn't work anymore. The cells lose their colour within days and do not grow. Temperature is fine (15--30 °C), pH is neutral ot basic (7.5-8.5), the medium is the one we successfully used in the lab before, the light in the greenhouse is not too strong (max. 200 umul m-2 s-1). What is going on? I wouldn't be surprised if it takes a while for them to start growing, but why do they lose their colour? Any insight would be greatly appreciated.
-> I prefer information from people with hands-on experience. I say this, because the last time, people just sent me links to publications which were rather off-topic.
Thank you very much!
Hi Ana, thanks for reaching out. We cultivated the two species one after the other. The reactor was cleaned in between and carefully rinsed with water. We repeat now the cultivation in the lab using the water from the reactor to see whether the presence of a harmful substance in the medium is a possibility.
One of the largest challenges in scaling cultures to outdoor systems is the process of photobleaching and photoinhibition. This occurs very frequently if the concentration of the inoculum is too low. I typically keep my biomass density above 0.1 g/L of ash-free dry weight. This allows for self-shading of the culture to reduce the impact of high light intensities.
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