What is the optimal sampling method for modeling of microalgae growth?

Question

Recently, I am performing microalgae (Chlorella sp.) cultivation experiments for the mathematical modeling of microalgae growth with respect to time.

The main issue is that an analysis of lipid contents in microalgae requires a large volume of culture media per data point. Especially, in the early stage of the cultivation, the density of the microalgae is very low, so almost 20% of the total culture media needs to be consumed for obtaining just a single data point. Due to this limitation, sometimes, I measured only three times (the beginning, middle, and last).

More data points are obviously desired for the accurate modeling but it ends up with huge loss of the media. This may affect the quality of the overall experimental results. This seems like a sort of trade-off. The problem is that I cannot increase the size of the reactor volume at the moment.

Could anybody recommend how to come up with the optimal sampling number in this situation?

Any experience, ideas or recommended papers are welcome.

Thank you.

Answer 1

For these kind of experiments, especially when you talk about modelling, it can be worth to set up a chemostat or at least a turbidostat. An example of such a study can be found in: Simultaneous growth and neutral lipid accumulation in microalgae by Klok et al. (Pubmed).

Alternatively you can use lipid dyes such as Bodipy but these are often very tricky to get to work and they might not penetrate in your Chlorella. Nile Red in any case is almost impossible to get working quantitatively despite it being used quite extensively, see details in this publication. Be very cautious when going down this route.