## 4 Discussion  
The phylogenetic analysis of the ribosome gene 18s rRNA from the NCYC1146 strain was made with a fragment of similar size to that described by [PERSON] et al. [19]. The NCYC1146 strain could be considered as a species of marine _Rhodotorula_ sp., owing to the genetic similarity with the NCYC4007 strain (Figure 1) described by [PERSON] et al. [9]. Despite the genetic similarity between NCYC4007 and NCYC1146, both strains can produce different substances that can be associated with the functional variability of the microorganisms when confronted by different environmental conditions. In this case, NCYC4007 comes from a temperate ecosystem with strong winds during upwelling periods [25], while  
Figure 4: Average production \(\pm\) SD of metabolic parameters determined for the NCYC4007 and NCYC1146 strains, cultivated in RGM at 15 °C. (**a,b**) Docosahexaenoicenoic acid production (DHA), total carotenoids (TC), live microbial biomass (ATP) and cell count of strains NCYC4007 and NCYC1146, respectively. (**c,d**) Intracellular glucose concentration and in the culture media, total phosphorus and intracellular cholesterol of strains NCYC4007 and NCYC1146, respectively. (**e,f**) Enzymatic activities of MDH and LDH of the strains NCYC4007 and NCYC1146, respectively. NCYC1146 is significantly different, isolated in a cold ecosystem with a high level of fresh water associated with adjacent rivers coming from the melting of snowdrifts and the high level of lignocellulosic material from a forestry origin [26]. This is the first report of marine _Rlodotorula_ strains that can grow using raw glycerol as a carbon source. No inhibitory effects compared with analytical grade glycerol were observed. Using raw glycerol, the concordance observed between the significantly higher production of biomass and growth parameters at 15 \({}^{\circ}\)C (optimum growth temperature) for the marine _Rlodotorula_ sp. NCYC4007 and NCYC1146 could be the result of a greater glycerol bioconversion to biomass compared to glucose. Non-marine _Rlodotorula_ (_R. glutinis_, _R. mucilaginousa_ and _R. gracilis_) showed that glycerol can be used to produce simultaneously lipids and carotenoids; nevertheless, a glycerol concentration higher than 10% can significatively decrease the growth rate [6; 7]. _R. gracilis_ seems to be a promising candidate for lipids and carotenoids production using low-cost wastes [8], with similar yields to the present study, but at a low sodium concentration. In the present study, the marine origin of the strains used can be an advantage to cope with the osmotic stress compared with non-marine _Rlodotorula_. In other marine microorganisms studied to produce lipids, such as _Thraustochytrium_ sp. AMCQS5-5, it can produce a biomass eight times greater in the medium that contains glycerol instead of glucose as a carbon source [12]. In addition, in marine yeasts such as _Yarrowia lipolytica_ has been described that the glycerol presents a higher absorption rate than the glucose, because glycerol passes into the microbial cell by facilitated diffusion and is assimilated via either the phosphorylation or the oxidative pathway [16; 27]. The production of DHA registered in strain NCYC4007 (23% in ODW) is similar to those registered for _Thraustochytrium_ sp. (20.4% in ODW; [28]), _Schizochytrium_ KH105 (22% in ODW [29]) and _Schizochytrium limacinum_ SR21 (19.5 at 22% in ODW [30]). In addition to these three tested media, the maximum production of DHA was observed between 144 and 216 h of cultivation, a greater time as described (96 to 120 h) for the _Thraustochytrium_ sp., _Schizochytrium_ KH105 and _Schizochytrium limacinum_ SR21 strains. In all carbon sources tested, a higher percent of UFAs than SFAs was observed in the fatty acids profile. Nevertheless, when raw glycerol is used, the lowest percentage of UFAs was observed. The change in the percentage of UFAs and SFAs as a result of the carbon source used has been reported in other oleaginous microorganisms such as _Rlodosporidium_ sp.