Picochlorum celeri as a model system for robust outdoor algal growth in seawater

With fast growth rates, broad halotolerance and the ability to thrive at high temperatures, algae in the genus Picochlorum are emerging as promising biomass producers. Recently, we isolated a remarkably productive strain, Picochlorum celeri, that attains > 40 g m−2 day−1productivities using simulated outdoor light. To test outdoor productivities, Picochlorum celeri was cultivated in 820 L raceway ponds at the Arizona Center for Algae Technology and Innovation. Picochlorum celeri demonstrated the highest outdoor biomass productivities reported to date at this testbed averaging ~ 31 g m−2 day−1 over four months with a monthly (August) high of ~ 36 g m−2 day−1. Several single day productivities were > 40 g m−2 day−1.

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Fig:  Outdoor pond productivity, temperature and light: (A) Harvest-to-harvest average areal biomass productivity, (B) volumetric AFDW, (C) daily minimum and maximum pond temperatures and (D) the daily PAR insolation for the 2020 outdoor field trial. Cultures were grown in nitrogen-replete medium in outdoor ponds located in Mesa, AZ. For areal productivity (A) and volumetric biomass concentration (B) and pond temperature (C), each datapoint represents the average of three ponds (n = 3) and standard error of mean. The period for which media salt concentrations are either 35 PPT or 50 PPT is shown by a horizontal line and arrowheads (in grey) in (A). Dotted line in (A) denotes 40 g m−2 day−1. PAR insolation (mol photons m−2 d−1) received by the ponds each day over the duration of the outdoor campaigns (D).

Importantly for sustainability,Picochlorum celeri achieved these productivities in saline water ranging from seawater to 50 parts per thousand sea salts, without any biocides or pond crashes, for over 143 days. Lastly, we report robust genetic engineering tools for future strain improvements.

Krishnan, A., Likhogrud, M., Cano, M. et al. Picochlorum celeri as a model system for robust outdoor algal growth in seawater. Sci Rep11, 11649 (2021). https://doi.org/10.1038/s41598-021-91106-5

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