## 2 Materials and Methods
### Analytical Methods  
Biomass concentration (dry weight) was monitored by measuring optical intensity (OD) at 750 nm [13], while at the end of the experiments, biomass dry weight was also directly estimated (filtered biomass was dried for 2 h in 70 \({}^{\circ}\)C). Carbohydrates were measured by a modified phenol-sulfuric acid method [14]: briefly, in 0.5 mL of cell suspension containing 10-50 mg/L carbohydrates, 10 \(\upmu\)L of 90% liquefied phenol was added, mixed and followed by the addition of 1.25 mL of 96% sulfuric acid. After 30 min, at room temperature, OD was measured at 485 nm. Lipids were measured by a modification of the sulfo-vanillin method [15]: briefly, 20 \(\upmu\)L of cell suspension containing 200-500 mg/L of lipids (in order to achieve these concentrations in the samples, biomass was concentrated by centrifugation) were added in 0.4 mL 96% sulfuric acid and then samples were placed in boiling water for 10 min. Next, samples were left at room temperature for 15 min to cool down and followingly 1.0 mL of phosphoric-acid/vanillin solution was added (0.12 g of vanillin was firstly dissolved in 5 mL of absolute ethanol, then in 15 mL DI water and finally 80 mL of 85% phosphoric acid were added). The samples were incubated at 37 \({}^{\circ}\)C for 15 min and OD was measured at 530 nm. Proteins were assayed according to [PERSON], et al. [16]: briefly, samples of 1.5 mL were centrifuged and the pelleted biomass was resuspended in 0.5N NaOH and incubated in an agitated heating plate for 15 min. A sample of 100 \(\upmu\)L of extracted proteins were then added to 100 \(\upmu\)L SDS 5% followed by the addition of 1 mL of a solution of 2% Na\({}_{2}\)CO\({}_{3}\) in 0.1N NaOH. After 15 min freshly diluted (1:1 with DI water) 2N Folin & Ciocalteu reagent was added and samples were left for 30 min in dark. OD was measured at 750 nm. Phycocyanin was extracted in 0.1M phosphate buffer (pH 7) by successive cycles of freezing and thawing biomass. The extracted phycocyanin concentration was measured spectrophotometrically and calculated as Phycocyanin \(\left(\text{mg/L}\right)=\frac{\text{OD}_{652}-0.474\times\text{OD}_{652}}{5.34}\)[17]. The pigment concentration was measured according to the following equations [18]:  
\[\text{Chl}_{\alpha}\left(\text{mg/L}\right)=16.82\,\times\,\text{OD}_{665}-9.28 \,\times\,\text{OD}_{652}\]  
and  
\[\text{Total carotenoids}\left(\text{mg/L}\right)=\frac{1000\,\times\,\text{OD}_{470 }-1.91\text{Chl}_{\alpha}-95.15(36.92\,\times\,\text{OD}_{652}-16.54\,\times \,\text{OD}_{665})}{225}\]  
All biomass composition analyses were performed after washing the samples for several times with deionized H\({}_{2}\)O. Dry algal biomass was measured indirectly spectrophotometricallyat 750 nm. All spectrophotometric determinations were carried out in Cadas 50 ([PERSON], Germany) spectrophotometer and analyses were carried out at least in triplicates for each replicate. The data given are their averages (n = 6). Quantum yield was measured in dark adapted cells (for 20 min) using a handheld chlorophyll fluorometer (AquaPen-C, PSI, Czech Republic). Light color was set at red-orange (630 nm) and the chlorophyll fluorescence was induced using actinic illumination of 1000 mol/m\({}^{2}\)/s. This light color is intended for excitation through phycobilins and therefore is suitable for measuring cyanobacterial cultures. Since the cultures were performed under non-aseptic conditions in order to evaluate the competition between _A. platensis_ and potential bacteria that would grow on glycerol too, the biomass of _A. platensis_ was estimated after its centrifugal separation from the bacteria biomass via the combination of gravitational forces and cell size. It was observed that biomass of _A. platensis_ after centrifugation was separated in the bottom of the tubes, whereas bacteria were visible as cream-colored body in the upper layer above _A. platensis_. Thus, the upper part of the pellet was carefully collected.