Elsevier

Journal of Biotechnology

Volume 336, 10 August 2021, Pages 56-63
Journal of Biotechnology

Towards industrial production of microalgae without temperature control: The effect of diel temperature fluctuations on microalgal physiology

https://doi.org/10.1016/j.jbiotec.2021.06.017Get rights and content
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open access

Highlights

  • Microalgae growth in photobioreactors is impacted by diel temperature cycles.

  • Picochlorum sp. (BPE23) showed growth up to a peak day temperature of 47.5 °C.

  • Maximum productivity was achieved with a daily peak temperature of 40 °C.

Abstract

Regions that offer high levels of sunlight are ideal to produce microalgae. However, as a result of high light intensities, the temperature in photobioreactors can reach temperatures up to 50 °C. Control of temperature is essential to avoid losses on biomass productivity but should be limited to a minimum to avoid high energy requirements for cooling. Our objective is to develop a production process in which cooling is not required. We studied the behaviour of thermotolerant microalgae Picochlorum sp. (BPE23) under four diel temperature regimes, with peak temperatures from 30 °C up to a maximum of 47.5 °C. The highest growth rate of 0.17 h−1 was obtained when applying a daytime peak temperature of 40 °C. Operating photobioreactors in tropical regions, with a maximal peak temperature of 40 °C, up from 30 °C, reduces microalgae production costs by 26.2 %, based on simulations with a pre-existing techno-economic model. Cell pigmentation was downregulated under increasingly stressful temperatures. The fatty acid composition of cell membranes was altered under increasing temperatures to contain shorter fatty acids with a higher level of saturation. Our findings show that the level of temperature control impacts the biomass yield and composition of the microalgae.

Keywords

Microalgae
Photobioreactor
Picochlorum
Physiology
Temperature
Fatty acid

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