Microalgal lipid production : A comparative analysis of Nannochloropsis and Microchloropsis strains

The oleaginous genera Nannochloropsis and Microchloropsis are recognized for their lipid accumulation capacity. Microalgal lipid accumulation is triggered by nitrogen starvation, negatively affecting photosynthesis and growth. Moreover, light and temperature play pivotal roles in microalgal physiology, lipid accumulation and composition. This study focuses on comparing the responses of eight microalgal strains from Nannochloropsis (N. oceanica Necton, N. oceanica IMET1, Nannochloropsis. sp. CCAP211/78, N. oculata, and N. limnetica) and Microchloropsis (M. gaditana CCFM01, M.gaditana CCMP526, and M.salina) to light, temperature, and nitrogen availability. Biomass, lipid content and productivities were monitored under different light intensities (150 (LL) and 600 μmol photons m−2 s−1 (HL)) and temperatures (15, 25, 30℃) under nitrogen (N-) starvation and replete conditions. Under N-starvation and HL, N. sp. exhibited the highest lipid content (59%) and productivity (0.069 g L-1 day-1), while N. oculata had the lowest lipid content (37.5%) and productivity (0.037 g L-1 day-1) among the eight strains. Notably, M. gaditana CCFM01 achieved the highest EPA content (4.7%), contrasting with N.oceanica IMET1 lowest EPA content (2.9%) under 150 μmol photons m−2 s−1 and N-repletion. The response to temperature fluctuations under LL was strain-dependent. Microchloropsis salina and M. gaditana CCFM01 demonstrated the highest and lowest lipid productivities (0.069 g L-1 day-1 and 0.022 g L-1 day-1, respectively) at 15℃ under N-starvation. Moreover, significant EPA accumulation across various strains was observed in N. oculata (5.7%) under N-repletion at 15°C, surpassing M. gaditana CCFM01 by 40%. Ultimately, the physiological responses to cultivation conditions vary markedly among microalgal strains, even within the same genus or species. This knowledge is essential for selecting suitable strains for the efficient microalgal lipid production industry. Graphical Abstract: Optimi zing cultivation conditions for the maximal lipid production in Nannochloropsis andMicrochloropsis (Figure presented.)