The cultivation conditions of S. almeriensis were identical to the description provided in [15]. In brief, the biomass was cultivated in Arnon medium in a 25 L bubble column annular bioreactor illuminated 24 h at 250 μ·mol−2·s−1 with temperature maintenance at 25 °C. Supply of air and CO2 was provided at a rate of 5000 cm3·min−1 and 25 cm3·min−1, respectively. The pH was fixed at 8. The cultivation lasted for 5 days.

Harvest was carried out using a separator (STC 3–06-170, GEA Westphalia, Germany). The resulting biomass paste was re-suspended with deionized water with a twofold purpose. First, to adjust the biomass concentration at ~ 100 g·L−1, i.e., as high as possible to reduce the energy input of the PEF-treatment. It has to be considered that the biomass needs to be still liquid enough to be pumped through the PEF treatment chamber. Second, to reduce the conductivity of the microalgae suspension from the initial 4.2 mS·cm−1 down to 1–1.2 mS·cm−1. The obtained conductivity corresponds to the design parameters of the treatment chamber for matched conditions and, therefore, ensures square electric pulses. As shown in the previous study, S. almeriensis is resistant to any osmotic shock resulting from this washing step [15]. The exact final concentration was determined by overnight drying of known amounts of the final suspension and supernatant in a drying oven (Universalshrank model U, Memmert, Germany) [40]. After each harvest, part of the biomass would be freeze-dried and stored in vacuum-sealed bags at -20 °C for composition determination of the biomass. Freeze-drying was conducted in a laboratory freeze-drier (Alpha 1–4 LDplus, Christ) for at least 24 h and stored afterwards in vacuum-sealed bags.

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