Strain-Specific Responses in Microalgal Lipid Production: Revealing the Impact of Light, Temperature, and Nitrogen Stressors on Nannochloropsis and Microchloropsis

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Abstract 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 species from Nannochloropsis(N.) and Microchloropsis(M.) genera (N. oceanica Necton, N. oceanica IMET1, N. sp. CCAP211/78, N. oculata, M. gaditana CCFM01, M. gaditana CCMP526, M. salina, and N. limnetica) to light, temperature, and nitrogen availability. Biomass, lipid content and productivities were monitored under light intensities (150 (LL) and 600μmol.m-2.s-1(HL)) and temperatures (15, 25, 30℃) variation under nitrogen(N-) starvation and replete conditions. Our results revealed that under N-starvation and HL, N. sp exhibited the most substantial lipid content (59%DW) and productivity (0.069glipid/L/d), while N. oculata had the lowest lipid content (37.5%DW) and productivity (0.037glipid/L/d) among the eight strains. Notably, M. gaditana CCFM01 achieved the highest EPA content (4.7%DW), contrasting with N. oceanica IMET1’s lowest EPA content (2.9%DW) under 150μmol.m-2.s-1 and N-repletion. The response to temperature fluctuations under LL was species-dependent. M. salina and M. gaditana CCFM01 demonstrated the highest and lowest lipid productivities (0.069 glipid/L/d and 0.022 glipid/L/d, respectively) at 15℃ under N-starvation. Moreover, significant EPA accumulation across various strains was observed in N. oculata (5.7%DW) under N-repletion at 15°C, surpassing M. gaditana CCFM01 by 40%. Ultimately, the physiological responses to cultivation conditions vary markedly among microalgal species, even within the same genus. This knowledge is essential for selecting suitable strains for the efficient microalgal lipid production industry.

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