## 2 Methods
### Analytical Methods  
Determinations of: glycerol concentration in the culture medium, dry cell weight (DCW) of microalgae, and lipid concentration in the biomass, as well as the qualitative analysis of microalgal biomass fatty acids were conducted following the methodology presented in our previous works [46; 47]. Crude glycerol concentration in the culture medium was determined by centrifugation (8000\(\times\)\(g\), 4 min, 10 \({}^{\circ}\)C; UNIVERSAL 320 R centrifuge, Hettich, Tuttlingen, Germany) and analysis of the supernatant using the Glycerol GK Assay Kit (Megazyme, Bray, Ireland). The concentration of nicotinamide adenine dinucleotide (NADH) was measured spectrophotometrically (Multiskan GO Microplate, Thermo Scientific, Vantaa, Finland) at a wavelength of 340 nm. The dry cell weight (DCW) of the microalgae was determined from the concentrated biomass that was washed twice with distilled water, then dried at 60 \({}^{\circ}\)C for 12 h in a moisture balance (MAR, Radwag, Poland) to stabilize the biomass. The lipid content of the biomass was determined by adding a hydrochloric acid solution to freeze-dried biomass (ALPHA 1-4 LD plus freeze dryer, Christ), which was then placed in a water bath (GFL 1003) at 75 \({}^{\circ}\)C for 40 min. The sample was treated with n-hexane for lipid extraction and placed in a vacuum evaporator (Hei-VAP Advantage G3, Heidolph, Schwabach, Germany) to evaporate the solvent. The lipid content of the sample was measured gravimetrically. The determination of fatty acids was done using a modified direct transmethylation method. The organic phase containing fatty acid methyl esters (FAME) was harvested and analyzed by chromatography (Clarus 680 GC (Perkin Elmer, Waltham, MA, USA) gas chromatograph) [46; 47]. Culture viscosity was determined using a Cannon-Fenske capillary viscosimeter (SCHOTT, Mainz, Germany). The k\({}_{\text{L}}\)a value was determined using a method described by [PERSON] et al. (2001) [40]. To this end, two solutions were prepared, including a supernatant of the culture medium and a solution of marine salt having the same concentration as in the culture medium (reference solution). To decrease partial pressure to 2% in both solutions, they were flushed with nitrogen. Then, each solution was aerated at the rate of 5 dm\({}^{3}\)/min and mixed at the speed of 300 rpm. The k\({}_{\text{L}}\)a value was determined as the inclination of the curve of partial oxygen concentration in the solution dependence on time. Samples (5 cm\({}^{3}\)) of the _Schizochytrium_ sp. culture were collected, transferred to a centrifuge tube, and centrifuged at a room temperature for 12 min at 15,000\(\times\)\(g\) (UNIVERSAL 320 R, Hettich). After completed centrifugation, the supernatant was determined for the concentration of saccharides representing the polymeric part of EPS, i.e., the so-called non-attached EPS [48]. The saccharides were isolated from the supernatant by 12-h precipitation \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Culture Variant** & **k\({}_{\text{L}}\)a** & **Turbine Speed** & **Volumetric Air** & **Bioreactor Tank** \\  & **[1/h]** & **[rpm]** & **Flow Rate** & **Volume** \\  & & **[dm\({}^{3}\)/h]** & **[dm\({}^{3}\)]** \\ \hline
1 & 150 & 185 & 0.80 & 20.0 \\
2 & 300 & 370 & 1.60 & 20.0 \\
3 & 450 & 555 & 2.40 & 20.0 \\
4 & 600 & 740 & 3.20 & 20.0 \\
5 & 750 & 925 & 4.00 & 20.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The k\({}_{\text{L}}\)a values and conditions of _Schizochytrium_ sp. culture mixing and aeration used in the study. in cold ethanol (\(-20\)\({}^{\circ}\)C), the final concentration of which after sample addition reached 80%, and then by nitrogen drying. Afterward, their concentration was determined using the phenol-sulfate method [49]. To this end, a 1-cm\({}^{3}\) sample of precipitated polysaccharides dissolved in distilled water was collected, to which 1 cm\({}^{3}\) of a 5% phenol solution was added, and the whole sample was mixed at the speed of approximately 1250 rpm (Vortex Reax top, Heidolph).