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Algae day and night cycles

Success goal

This experiment will show the growth curve of algae over a 20h:4h day/night cycle, at two different intensities (4% and 8%).

Requirements​

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  • At least one available Pioreactor
  • Algae
  • Media for algae; for ex. Bold's Basal Medium (BBM)
  • Two LED cables per Pioreactor.

Introduction​

Adding two LED bulbs onto your base Pioreactor will transform it into a photo-bioreactor, giving you the ability to grow species that require light! In this experiment, we will monitor algae using our Day/Night plugin.

There are two main phases that will be observed between the light being on ("day") and off ("night"). Exponential growth will occur during the “day” as algae biomass is accumulated through photosynthesis), and stalled growth will occur “overnight”, where algae reproduce, but don't accumulate biomass. This should make for some interestingly patterned OD readings!

Experiment​

We started off with a culture of Chlorella vulgaris that we grew in a tissue culture flask using Bold's Basal Medium. We then used 10 mL of BBM per vial, then inoculated with 1 mL of our culture. With two Pioreactors, we started our experiment using the Day/Night plugin and chose light intensities of 4% and 8%. We kept stirring high to avoid formation of flocculants that could impede our OD readings.

Typical experiments use a 16h:8h day night cycle, but we've adjusted the time period to 20h:4h. The experiment takes place over a few days, so results were seen after a week.

Results​

For this style of experiment, let's investigate our normalized OD results:

Adjusting just one factor (light intensity) where one is twice as high as the other yielded an approximate doubling of growth in the vial subjected to higher light intensity!

Recommendations​

Your Pioreactor is capable of controling a wide diversity of lighting effects on algae or other photosynthesizing microorganisms. The addition of the Day/Night cycle plugin and the ability to use LEDs opens a range of photobioreactor experiments! You can adjust intensities, photoperiods, and even switch out types of bulbs across the light spectrum to study effects of colours or UV lights.

Detailed procedure​

  1. Attach two LED cables into channels C and D.
  2. Insert the bulbs into the X2 and X3 pockets and secure them in place with the pocket caps. While on, some light leaking is acceptable.
  3. Prepare a sterile stock of media for algae. We used Bold’s Basal Medium (BBM). Aim for 10 to 12 mL of media per each vial/Pioreactor you will be using. This is to allow more headspace for oxygen!
  4. Add 1 mL of your algae culture to each vial.
  5. Wipe the vials and place them in the Pioreactor.
  6. Visit pioreactor.local and start a new experiment.
  7. Click the Plugins tab on the left and install the led_cycle plugin. This will add the Day/Night feature when you begin LED automations.
  8. On the left menu, select the Pioreactors page. Add any additional Pioreactors that you would like to use (more information here). Select Manage all Pioreactors, and start Stirring activity and OD reading activity.
Optional

Start the Temperature automation activity set on an optimal temperature.

  1. Start the LED automation at the bottom of the Activities list in Manage. Select Day/Night Cycle from the drop down menu, and set your desired Intensity (no more than 12% works best!) or Light and Dark duration (16h:8h is optimal).
    • This automation creates a day/night cycle ideal for algae growth.
  2. Confirm that everything looks normal on the Overview page (ex: receiving optical density signal).
  3. Back on the Pioreactors page, select Manage all Pioreactors and start Growth rate. It will take a minute for results to begin showing up.
Optional

Change the names of the Pioreactor in the UI to organize your vials.

  1. Watch the growth progress on the Overview page.