Spirulina - what next?

I’m not willing to admit defeat with the Spirulina, I managed to grow it OK prior to last week’s livestream, when I was pretty much following the instructions.

Why do you think it kept dying?

What do you think I should do next. Should I:

  • 1. repeat the 10ml culture media plus 5ml inoculum to see if we had some sort of inhibitor in last weeks culture
  • 2. pop 15ml of the remaining backup culture (that's currently in a 1L beaker) in and see if it grows
  • 3. set up a chemostat
  • 4. other..?
  • My suggestion would be 1., but 2. is okay as well. The process to get a good protocol will be iterative.

    I have a Spirulina culture arriving Monday, so I'll try some experiments locally, too. My process will be iterative: I'll set up an experiment with the best chance of success: decent initial density with a culture I know is healthy, warm environment (30C - 32C), moderate amount of light to avoid photo-inhibition or shading, ~500RPM. Goal is get some (any) growth. If that works, I'll try with less initial density. If that works, then try a chemostat, etc.

    @“CamDavidsonPilon”#p49 Yes, I think I’ll try 1 first, if that doesn’t work then 2, if either work I’ll try to go chemostat.

    I understand that pH is critical with spirulina. So I’ve asked on the [Pioreactor forum](https://forum.pioreactor.com/t/ph-probes-monitoring/178?u=martin) if anyone has managed to hook up a pH probe to theirs. While a [micro pH probe](https://www.fishersci.com/us/en/browse/90151107/micro-ph-electrodes) would easily fit in the 20ml Pioreactor, a more affordable solution may be to measure pH in the chemostat waste.

    Speaking of chemostat waste-stream monitoring, we had a great question in yesterday’s livestream about directly viewing Pioreactor cultures with the [OpenFlexure](https://openflexure.org) microscope. We discussed making a PDMS flow-through cell when I returned my loaner.

    So how do we measure cyanotoxins? One of the biggest benefits of 20ml spirulina cultures would be determining the optimal conditions for spirunlina growth. A key thing here would be minimisation of cyanotoxin production.

    [Microcystins and Cyanobacterial Contaminants in the French Small-Scale Productions of Spirulina (Limnospira sp.)](https://www.mdpi.com/2308878) found a wide range of microcystins in French Spirulina products, but concluded that consuming the producers' general recommendation of 3g spirulina per day would on average result in a microcystin intake 4x below the WHO chronic exposure levels. This would raise concerns if anyone considered using spirulina as a primary protein source, given the [BHF recommendation](https://www.bhf.org.uk/informationsupport/heart-matters-magazine/nutrition/protein#:~:text=How%20much%20protein%20do%20I,%2C%20or%2055g%20for%20men) of 0.75 g protein per kg body-weight.

    If we were to investigate microcystin production we would need a means of detection of microcystins the [US EPA list](https://www.epa.gov/ground-water-and-drinking-water/detection-methods-cyanotoxins) numerous techniques requiring equipment only likely to be found in very well funded research laboratories.

    [A Mini-Review on Detection Methods of Microcystins](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7601875/) raises the hope of emerging biosensors. We should investigate whether any available technologies may make this research affordable.

    pH is coming to the Pioreactor! Unfortunately @CamDavidsonPilon and I bought different pH boards - my fault for not mentioning the result of my investigations. Even so, it’s great to hear that Cam’s working on the software. It’s particularly good news for all the Spirulina researchers - I’m not convinced we could fit a pH probe along with 2 electrodes and a sparging tube in a 20ml pioreactor vial for HOB[1] research.

    1. Hydrogen Oxidising Bacteria ↩︎