## 3 Results and Discussion
As shown in Figure 7, significantly more astaxanthin could be extracted into ethyl acetate in heterotrophic culture 9 (15.0 mg L\({}^{-1}\)), germinated without an external carbon source, and heterotrophic culture 10 (24.8 mg L\({}^{-1}\)), germinated with more glucose than in the phototrophic culture 11 (7.5 mg L\({}^{-1}\)) and mixotrophic culture 12 (8.3 mg L\({}^{-1}\)), 49 h after the start of germination. Similar to mixotrophic culture 4 (8.9 mg L\({}^{-1}\)) and phototrophic culture 2 (7.2 mg L\({}^{-1}\)), more astaxanthin could be extracted into ethyl acetate at mixotrophic conditions of culture 12 (8.3 mg L\({}^{-1}\)) compared to the phototrophic conditions of culture 11 (7.5 mg L\({}^{-1}\)). As shown in Figure 8, 49 h after the start of germination, 33% of the cells were in the zoospore stage in the mixotrophic culture 12 and 28% were in the zoospore stage in the phototrophic culture 11. In heterotrophic conditions with additional glucose (culture 10), 82% of the cells were in the zoospore stage, whereas without an external carbon source (culture 9) 62% were present at this cell stage, 49 h after the start of germination. According to the data presented in Figure 7 for heterotrophic culture 10, germinated at ambient air approx. 70% more astaxanthin could be extracted into ethyl acetate than in the heterotrophic culture 9, germinated without an external carbon source, 49 h after the start of germination. Figure 7: Astaxanthin concentration in the ethyl acetate extract of the heterotrophic culture 9 (heterotrophic + “no external carbon source” + ambient air) and culture 10 (heterotrophic + 4 mM glucose + ambient air), phototrophic culture 11 (phototrophic + ambient air + 75 umol m\({}^{-2}\) s\({}^{-1}\)) and mixotrophic culture 12 (mixotrophic + 4 mM glucose + ambient air + 75 umol m\({}^{-2}\) s\({}^{-1}\)) at different time points after the start of germination; data obtained by single determination. As presented in Figure 9, the initial astaxanthin content in the cyst biomass of culture 9-12 was 1.51 wt.% and no decline of the astaxanthin content in the biomass was measured at heterotrophic conditions without an external carbon source (culture 9) and with glucose (culture 10). In culture 10, an increase of the astaxanthin content to 2.28 wt.% was measured 49 h after the start of germination, with a relative standard deviation of 36%. Similar to the previous set of experiments, the astaxanthin content in the biomass at mixotrophic conditions (culture 12) fell slightly in the course of germination (\(p>0.05\)) to 1.11 wt.% 149 h after the start of germination, and the astaxanthin content of the phototrophic culture 11 decreased slightly to 1.42 wt.% (\(p>0.05\)). A stronger decrease of the astaxanthin biomass content in \(H\). _pluvialis_ at higher light intensity compared to germination without light has already been described in the literature. There, the astaxanthin content decreased from 454 initially to 46 pg cell\({}^{-1}\) for phototrophic illuminated cells at 240 umol m\({}^{-2}\) s\({}^{-1}\) and 116 pg cell\({}^{-1}\) for heterotrophic cultures (without external glucose) [29]. Figure 8: Relative distribution of the cell stages of \(H\). _pluvialis_ at different points in time after the start of germination for the heterotrophic culture 9 (heterotrophic + \"no external carbon source” + ambient air) and culture 10 (heterotrophic + 4 mM glucose + ambient air), phototrophic culture 11 (phototrophic + ambient air + 75 μmol m\({}^{-2}\) s\({}^{-1}\)) and mixotrophic culture 12 (mixotrophic + 4 mM glucose + ambient air + 75 μmol m\({}^{-2}\) s\({}^{-1}\)). Figure 9: Time course of the biomass concentration and the astaxanthin content in the algal biomass of heterotrophic culture 9 (heterotrophic + \"no external carbon source” + ambient air) and culture 10 (heterotrophic + 4 mM glucose + ambient air), phototrophic culture 11 (phototrophic + ambient air + 75 μmol m\({}^{-2}\) s\({}^{-1}\)) and mixotrophic culture 12 (mixotrophic + 4 mM glucose + ambient air + 75 μmol m\({}^{-2}\) s\({}^{-1}\)).