I'm growing Scenedesmus in a small reactor (about 3 litres). After 5 days of cultivation, the alga starts to stick on the walls of the reactor and precipitate out to form a bunch of precipitates. How can I avoid this precipitation?
Autoclave the phosphorus separately and put the solid carbon sources in the oven at 120 degrees celcius overnight then mix them with sterilized water this is before inoculation.
Stress conditions e.g. nitrogen depletion can cause some algae to precipitate or adhere to the wall of a bioreactor. Also make sure you have a really good mixing of the culture. I find stirring shafts more effective at stopping algae from sedimentation.
Some micronutrients metals in high concentrations can make Scenedesmus to precipitate, like Cu, Co. Check you concentration. Also pH needs to be around 7-8 at the start. If your pH goes up to fast due to growth it can make the alga precipitate
when you use Intense aeration fast growth happens and then pH goes up. you can decrees the Aeration intensity.
Is it posible to have in Your cultivation system a permanent flux of nutrient and of course a release of cells or is it a simple reactor? In the latter case, some nutrient (nitrogen for instance) could decrease and sometimes cells could porduce polysaccharids with stick the cells....moreover, when some cell density are reached the growth should decrease ..
What kind of culture is it? Axenic, unialgal? I grown a Scenedesmus sp. before, that I isolated from a local water stream, in cylindrical tanks (5-7L). The induction of stressful conditions, sometimes, lead to an agglomeration and precipitation of algae due to bacteria/fungi flora growth. That can be avoided with appropriate medium and culture conditions. The aeration on the bottom was also critical. Good aeration flow helps prevent agglomeration and film formation on the walls of the tank, maintaining the circulation of the whole culture.
And we can't forget that a proper inoculation with enough volume of healthy and high in density inoculum makes all the difference too.
Good luck
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