Operation of Laboratory Photobioreactors with Online Growth Measurements and Customizable Light Regimes

This protocol enables replicated microalgae experiments with little user input. It is designed for researchers looking to upgrade from manually monitored to bench top flasks without purchasing technical and expensive commercial photo bio reactors. This photo bio reactor enables light ratio and flexibility, continuous growth monitoring, and triplicate replication.

To begin, open the data acquisition software. Fill in the configuration page and assign calibration files to their respective sensors. Under the directory file name, select the corresponding digital input module port number folder.

Click on the current folder and repeat for all ports. Then click on okay to move on to the logging page. Next, fill the glass bottles to the desired volume with the cultivation medium and centrifuge the stock culture in three balanced 50 milliliter tubes to yield three pellets.

Add one pellet to each bottle using a serological pipette and fresh medium. Then drop a 25 by eight millimeter magnetic stirrer into each bottle before sealing the bottle opening with a rubber stopper and threaded aperture screw cap. If any optional sampling ports are installed, close the valves.

After locating the end of each gas line inside the PVC pipe, attach a needle to the valve's mail lure port. Connect each bottle to its gas sensor by piercing each rubber stopper with the corresponding needle. Then, launch each gas sensor individually by checking the tick box on the left side of the screen, clicking on start, and inputting a file name.

Click okay and repeat for all sensors. Next, switch on the photo bio reactor and ensure that the digital multiplex lighting controller is plugged into a power supply. Using the button on the digital multiplex controller, switch between the helper scene and the customized light scene to ensure the device is functioning correctly.

For bottle sampling, prepare an additional 500 milliliters of the fresh medium before commencing the experiment. To collect the sample, close the valve on the gas line and connect a 10 milliliter syringe to the sampling port valve. After connecting the syringe, open the sampling port valve and withdraw eight milliliters of culture.

Then close the sampling port valve and disconnect the syringe. Next, connect to syringe containing eight milliliters of fresh medium to the sampling port valve. Then open the valve and inject the fresh medium.

Finally, close the sampling port valve and disconnect the syringe. To export the data, select file and offline data. After selecting all relevant log files, export the data to spreadsheet software and save.

A successful experiment is characterized by a closely replicated diurnal pattern of oxygen production. The oxygen flow rate acts as a proxy for a culture's growth rate. During illuminated hours, gas production steadily increases and during non illuminated hours, gas production stops.

The total volume of oxygen produced over four days ranged from 316 milliliters in treatment A to 902 milliliters in treatment C.In the 300 micro mole per meter squared per second light regime, the temperature increased by a maximum of 1.4 degrees Celsius during the day. Culture temperatures returned to baseline overnight. Despite differing in their initial biomass concentrations, treatments B and C generated the same amount of total biomass causing identical shifts in medium pH.

The online oxygen flow rate data revealed that each treatment had varying daily growth rates, which was also reflected in the twice daily pH measurements. On day one, treatment B's growth rate was lower than that of treatment C.Whereas by day three, treatment B's growth rates surpassed that of treatment C.Oxygen flow rate data indicated that the highest growth occurred on day three in treatment B.Growth estimates based on total measured oxygen were expected to slightly underestimate biomass growth which was valid for five out of seven examples. Two examples overestimated growth.

This may have been influenced by experiments being determined at the end of the night. Substantial nighttime respiration enhances oxygen consumption, generates a bottle head space vacuum, sucking in pack with liquid from gas sensors. If respiration may be high, we opening the head space overnight.