## 2 Materials and Methods
### Preculture and Cultivation Protocol  
Precultures were produced in 400 mL bubble column PBRs with a working volume of 200 mL [24]. The PBRs were placed inside an incubator (Protors, Infors HT, Bottmingen, Switzerland) running at 25 \({}^{\circ}\)C. The gas flow rates were adjusted manually to ensure sufficient mixing; the gas consisted of compressed air mixed with 2% CO\({}_{2}\). Illumination from above was realized by six fluorescent tubes with an average photon flux density of 85 umol m\({}^{-2}\) s\({}^{-1}\). If the offline measured pH was outside the range 7.5-pH 8.5, the pH was adjusted manually with either 0.5 M NaOH or 0.5 M HCl, as required. When a cell density of OD\({}_{750}\) above 3.0 was measured, a new preculture was inoculated with an OD\({}_{750}\) of 0.15. Precultures with an OD\({}_{750}\) of approximately 2 were diluted with ASW medium to a designated OD\({}_{750}\) of 0.5. An amount of 10 mL of the cell suspension was then distributed into the parallel stirred-tank bioreactors. The parallel mL-scale stirred-tank bioreactor unit was placed inside an LHS for automated OD and pH measurement, pH correction, liquid level adjustment and droplet supplant. The microalgae cell suspension was agitated at 500 rpm with magnetically induced S-stirrers. Agitation was automatically stopped for sampling and liquid level detection. The 48 parallel stirred-tank bioreactors were gassed by 288 L h\({}^{-1}\) of air with 2% CO\({}_{2}\). Headspace cooling of the parallel bioreactors was set to 14 \({}^{\circ}\)C.  
The cultivation temperature was a constant 29 \({}^{\circ}\)C as long as microalgae growth was being studied at constant illumination. Studies based on day and night cycles of incident light and temperature used the weather data of a summer day in June 2012 in Almeria, which were repeatedly applied. Because of its high solar irradiance, warm air temperature, and infrastructure, the seaside town of Almeria is an ideal reference location for outdoor microalgae cultivation [31]. The light intensity was automatically adjusted every ten minutes. The temperatures of all parallel bioreactors were adjusted automatically with a step time of 1 h, in line with the air temperature of the summer day in Spain (6 a.m.: 13.9 \({}^{\circ}\)C, 7 a.m.: 18.3 \({}^{\circ}\)C, 8 a.m.: 21.2 \({}^{\circ}\)C, 9 a.m.: 25.5 \({}^{\circ}\)C, 10 a.m.: 27.6 \({}^{\circ}\)C, 11 a.m.: 28.8 \({}^{\circ}\)C, 12 a.m.: 27.9 \({}^{\circ}\)C, 1 p.m.: 28.6 \({}^{\circ}\)C, 2 p.m.: 29.4 \({}^{\circ}\)C, 3 p.m.: 29.1, 4 p.m.: 29.1 \({}^{\circ}\)C, 5 p.m.: 28.3 \({}^{\circ}\)C, 6 p.m.: 27.9 \({}^{\circ}\)C, 7 p.m.: 26.6 \({}^{\circ}\)C, 8 p.m.: 24.9 \({}^{\circ}\)C, 9 p.m.: 22.8 \({}^{\circ}\)C, 10 p.m.: 21.8 \({}^{\circ}\)C, 11 p.m.: 20.9 \({}^{\circ}\)C, 12 p.m.: 16.8 \({}^{\circ}\)C, 1 a.m.: 17.5 \({}^{\circ}\)C, 2 a.m.: 17.1 \({}^{\circ}\)C, 3 a.m.: 15.8 \({}^{\circ}\)C, 4 a.m.: 15.1 \({}^{\circ}\)C, 5 a.m.: 14.6 \({}^{\circ}\)C). At-Line and Offline Measurement of Optical Densities, Determination of Cell Dry Weight Concentration and Growth Rate  
For at-line OD\({}_{750}\) measurements, the LHS (Microlab STARlet, Hamilton Bonaduz AG, Bonaduz, Switzerland) sampled a 250 \(\upmu\)L cell suspension and performed a 1:5 and 1:25 dilution in a 96-well MTP (clear, flat bottom). The _M. salina_ cell suspensions were diluted with deionized water with 27 g L\({}^{-1}\) NaCl. Optical densities were measured automatically using an MTP photometer at 750 nm (Synergy HTX, multi-mode reader, Biotek, Winooski, VT, USA). Offline OD\({}_{750}\) measurements were performed with a cuvette photometer (Genesys 105 UVVis, Thermo Fisher, Waltham, MA, USA) with 10 mm cuvettes at 750 nm. To enable better comparison between OD\({}_{750}\) in preculture and stirred-tank PBRs, an OD\({}_{750}\) correlation was generated between the MTP and cuvette photometers. All results showed either directly measured or correlated cuvette OD\({}_{750}\). OD measurement at 750 nm is an established method for growth monitoring of microalgae [16; 57; 58].