Abstract
BackgroundThis batch study deals with the relation between lipid as well as triglyceride contents in Nannochloropsis salina and variation in culture conditions such as nitrogen concentration and temperature.ResultsThe tested parameters caused reduction in growth expressed as cell count, optical density and dry weight, as well strongly involved in lipids and triglycerides accumulation and significantly affected the lipid productivity. At the beginning of the work, the concentration of nitrogen in the medium was reduced to three quarter, half and quarter of the original f2 medium while the temperature kept constant. After that, the optimal nitrogen concentration (quarter of the original media) giving high lipid yield was tested with different temperature degrees from 15 to 35°C with five degree intervals. Although the growth was insignificantly influenced, a considerable increase in lipid and triglyceride (56.1 and 15.1% of dry weight respectively) was observed when the concentration of nitrogen in the medium was reduced to the quarter. Moreover, 59.3% lipid and 17.1% triglyceride on the basis of dry weight were obtained by the combination of 25% nitrogen concentration and 30°C. Simple regressions recommended that the interaction effect of nitrogen limitation and temperature on lipid and triglyceride accumulation was not as fundamental as for nitrogen limitation stress.ConclusionThe degree of nitrogen availability in the combination of temperature effect has been identified as the critical determinant for the maximal production of lipid in N. salina. Nevertheless, major advances in this field can be considered by studying more stresses techniques and genetic strategies.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0085-7) contains supplementary material, which is available to authorized users.
Highlights
This batch study deals with the relation between lipid as well as triglyceride contents in Nannochloropsis salina and variation in culture conditions such as nitrogen concentration and temperature
The highest cell number obtained was under control condition (9.9 × 106/ml culture) with 0.77 optical density, 0.61 g L−1 dry weight and 0.228 g L−1 day−1 lipid productivity
The lowest cell number, optical density and dry weight obtained were in medium with 25% nitrogen concentration (7.9 × 106/ml culture, 0.63 and 0.48 g L−1 respectively) with highest lipid productivity of 0.370 g L−1 day−1
Summary
This batch study deals with the relation between lipid as well as triglyceride contents in Nannochloropsis salina and variation in culture conditions such as nitrogen concentration and temperature. Algal biomasses are successfully produced with relatively low lipid contents. Optimization of biomass and lipid in microalgae has been studied in batch, closed and open outdoor systems (Zou and Richmond 2000; Sandnes et al 2005; Grobbelaar 2007). In those culture systems, the environmental parameters and nutrient supply were found to be vital factors for growth improvement and induction of lipid in microalgae. Many algae modify their lipid biosynthetic pathways to produce and accumulate neutral lipids, mainly in the form of triacylglycerol.
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