Climate-simulated Culturing in LEAPS Photobioreactors
The PNNL Laboratory Environmental Algal Pond Simulator (LEAPS) photobioreactors are used to determine the areal biomass productivity of TIER II DISCOVR strains under nitrogen-replete and nitrogen–deplete culture conditions simulating 20 cm deep outdoor ponds in Mesa, Arizona using winter and summer season light and temperature scripts for January 31st and July 1st, respectively. Mesa, AZ is the geographical location of the Arizona Center for Algae Technology and Innovation (AzCATI), and is the current Algae Biomass Productivity State of Technology (SOT) testbed site.
The LEAPS consists of six glass column bioreactors submerged in a temperature controlled water bath and illuminated from above with a high-intensity solar spectrum LED panel (Figure 1). The design, operation, and validation of the LEAPS using outdoor pond culture data is described in more detail in Huesemann et al. (2017). A video of the LEAPS in operation can be viewed here: https://marine.pnnl.gov/renewable.asp.
In the DISCOVR project, the LEAPS is operated at 20 cm culture depth using 30 year average light and temperature scripts generated by the PNNL Biomass Assessment Tool (Wigmosta et al., 2011) for January 31st and July 1st, for Mesa, Arizona (see Figures 2 and 3).
Arizona winter season light and temperature scripts
Arizona summer season light and temperature scripts
Three DISCOVR TIER II summer seasons strains (Chlorella sorokiniana DOE1116, Stichococcus minor CCMP819, and Scenedesmus obliquus UTEX393) were cultured in DISCOVR growth medium (possibly link to gradient incubator Research Area webpage where we could list the medium recipe) in the LEAPS photobioreactors, first under nitrogen-replete and then under nitrogen-deplete conditions, using the July 1 summer season script (see Figure 2).
Biomass concentration increased linearly with time during the two subsequent nutrient-replete growth phases (Figure 4). Following nitrogen-depletion between days 9 and 10 (Figure 5), the rate of biomass growth slowed down (Figure 4). The areal biomass productivity was calculated as the average of the four linear phase productivities during nutrient-replete culture conditions (Figure 6). The most productive strains emerging from the LEAPS experiments move forward to TIERIII. A ranking of all TIER II DISCOVR winter and summer season strains based on their areal biomass productivity in nutrient-replete LEAPS cultures can found in the LEAPS success story section
Average biomass concentration (Ash-free Dry Weight, AFDW) as a function of time for the three DISCOVR summer season strains cultured in the LEAPS using the Arizona summer season script. The salinity of the media were 0.4 ppt for Scenedesmus obliquus, 0.4 ppt for Chlorella sorokiniana, and 30 ppt for Stichococcus minor. The LEAPS cultures were harvested and restarted between Days 5 and 6. Error bars are one standard deviation (n=2).
Average ammonia nitrogen concentration as a function of time for the three DISCOVR summer season strains cultured in the LEAPS using the Arizona summer season script. Error bars are one standard deviation (n=2).
Average areal biomass productivity of the three DISCOVR summer season strains during the nutrient-replete linear growth phases in the LEAPS cultures using the Arizona summer season script. Error bars are one standard deviation (n=4).
Huesemann, M.H., P. Williams, S. Edmundson, P. Chen, R. Kruk, V. Cullinan, B. Crowe, and T. Lundquist, “Laboratory Environmental Algae Pond Simulator (LEAPS) Photobioreactors: Validation Using Outdoor Pond Cultures of Chlorella sorokiniana and Nannochloropsis salina”, Algal Research, 26:39-46, 2017.
Wigmosta, M.S., A.M. Coleman, R.J. Skaggs, M.H. Huesemann, and L.J. Lane, “National microalgae biofuels production potential and resource demand”, Water Resources Research, 47:2011.
Pacific Northwest National Laboratory, Marine Sciences Laboratory
Climate-simulated culturing, photobioreactors