Optimization of photosynthetically active radiation, temperature, and urea deprivation for increasing neutral lipids and fatty acids in Scenedesmus obliquus and Chlorella vulgaris as biodiesels

The present study investigated the impact of photosynthetically active radiation (PAR), culture temperature, and urea addition on the biomass, total lipid, lipidomic profile, and fatty acid productivity in Scenedesmus obliquus (S. obliquus) and Chlorella vulgaris (C. vulgaris) for sustainable biodiesels. In this study, S. obliquus and C. vulgaris, respectively, showed generally high cell densities with 1.23 g/L and 1.22 g/L of dried cell weights and 18.2% and 17.65% of lipids. Of the various PARs tested (10, 20, 40, and 60 mu mol/m2/sec), 60 mu mol/m2/sec showed maximal biomass yields for both species (1.78 g/L of dried cell weight and 25.7% of lipids for S. obliquus; and 1.74 g/L of dried cell weight and 24.6% of lipids for C. vulgaris). Of the various temperatures (27 degrees C, 37 degrees C, and 47 degrees C), 27 degrees C showed maximal dried cell weights (1.22 g/L for S. obliquus and 1.23 g/L for C. vulgaris), whereas 47 degrees C accu-mulated high levels of lipids (23.5% for S. obliquus and 21.6% for C. vulgaris). On the other hands, urea depri-vation in the medium increased lipid levels in both species compared to no deprivation (10% increase for S. obliquus and 8% increase for C. vulgaris). The fatty acid profile showed that palmitic acid with 16 carbons and double bonds was dominant among major fatty acids, accounting for 30.55% for S. obliquus and 26.6% for C. vulgaris. Furthermore, urea deprivation and 60 mu mol/m2/sec of PAR showed the highest proportions of unsat-urated fatty acids in both species (27.55% for urea deprivation and 30.55% for PAR in S. obliquus; and 28.33% for urea deprivation and 26.6% for PAR in C. vulgaris).

Automated summary

The present study investigated the impact of photosynthetically active radiation (PAR), culture temperature, and urea addition on the biomass, total lipid, lipidomic profile, and fatty acid productivity in Scenedesmus obliquus (S. obliquus) and Chlorella vulgaris (C. vulgaris) for sustainable biodiesels. Results showed that both S. obliquus and C. vulgaris exhibited high cell densities and lipid contents. The optimal parameters for biomass yields were a PAR of 60 μmol/m2/sec and a temperature of 27 degrees Celsius. Urea deprivation and a PAR of 60 μmol/m2/sec resulted in the highest proportions of unsaturated fatty acids in both species.