Thermal responses of Tetradesmus obliquus for industrial outdoor cultivation

In microalgae cultivation systems, fluctuating temperatures impact growth rates and biomass quality, whilst extremes of temperature can lead to the loss of large-scale cultures. Evaluation and selection of strains based on their performance under different temperatures could offer substantial improvements by reducing costs and increasing yields. Here the thermal performance of Tetradesmus obliquus UTEX393 was compared with a novel isolate of the same species, SNS0120, using turbidity-controlled flat-panel photobioreactors. UTEX393 showed higher growth performance at all temperatures and a higher thermal limit compared to SNS0120. Total fatty-acids were not influenced by temperature, but the fatty-acid profiles varied, and omega-3/6 ratios were lower under high temperatures. Transcriptomic analysis of UTEX393 showed that temperature caused substantial shifts in gene expression, with 4971 significantly differentially expressed genes during a temperature upshift from 10 °C (low temperature) to 25 °C (optimal temperature), and 3683 genes significantly differentially expressed from 25 °C (optimal temperature) to 34 °C (high temperature). [Display omitted] •Thermal sensitivity of T. obliquus isolates differed substantially.•Photosynthetic maximum quantum yield Fv/Fm was weakly temperature dependent.•The omega-3:omega-6 PUFA ratio decreased with increasing temperature.•Cell-wide changes in gene expression associated with higher growth rates at 25 °C.•Expression of genes for thermal stress responses at 34 °C