Abstract
BackgroundDecreasing fossil fuels and its impact on global warming have led to an increasing demand for its replacement by sustainable renewable biofuels. Microalgae may offer a potential feedstock for renewable biofuels capable of converting atmospheric CO2 to substantial biomass and valuable biofuels, which is of great importance for the food and energy industries. Parachlorella kessleri, a marine unicellular green alga belonging to class Trebouxiophyceae, accumulates large amount of lipids under nutrient-deprived conditions. The present study aims to understand the metabolic imprints in order to elucidate the physiological mechanisms of lipid accumulations in this microalga under nutrient deprivation.ResultsMolecular profiles were obtained using gas chromatography–mass spectrometry (GC–MS) of P. kessleri subjected to nutrient deprivation. Relative quantities of more than 60 metabolites were systematically compared in all the three starvation conditions. Our results demonstrate that in lipid metabolism, the quantities of neutral lipids increased significantly followed by the decrease in other metabolites involved in photosynthesis, and nitrogen assimilation. Nitrogen starvation seems to trigger the triacylglycerol (TAG) accumulation rapidly, while the microalga seems to tolerate phosphorous limitation, hence increasing both biomass and lipid content. The metabolomic and lipidomic profiles have identified a few common metabolites such as citric acid and 2-ketoglutaric acid which play significant role in diverting flux towards acetyl-CoA leading to accumulation of neutral lipids, whereas other molecules such as trehalose involve in cell growth regulation, when subjected to nutrient deprivation.ConclusionsUnderstanding the entire system through qualitative (untargeted) metabolome approach in P. kessleri has led to identification of relevant metabolites involved in the biosynthesis and degradation of precursor molecules that may have potential for biofuel production, aiming towards the vision of tomorrow’s bioenergy needs.
Highlights
Decreasing fossil fuels and its impact on global warming have led to an increasing demand for its replacement by sustainable renewable biofuels
Growth and biochemical analysis The primary impact of nutrient stress is visible on the growth pattern, so the biomass accumulation was analysed for P. kessleri under the nitrogen, phosphorousand sulphur-deprived conditions
The results demonstrated that this strain had severe effect on growth in nitrogen (N-) deprivation, i.e. growth was shunted within 4 days of deprivation after which no change in biomass was observed (Fig. 1a)
Summary
Decreasing fossil fuels and its impact on global warming have led to an increasing demand for its replacement by sustainable renewable biofuels. Microalgae may offer a potential feedstock for renewable biofuels capable of converting atmospheric CO2 to substantial biomass and valuable biofuels, which is of great importance for the food and energy industries. Shaikh et al Biotechnol Biofuels (2019) 12:182 development of sustainable renewable energy sources. Microalgae are being looked upon as a potential source for biodiesel production and have gained considerable attention because of their capability to utilize sunlight and water to convert atmospheric CO2 into biomass and biofuels which can prove to be important for both food and energy requirements [2, 3]
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