Document Type : Research Paper
Department of Biosciences and Bioengineering, Wadhwani Research Center for Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Department of Entomology & Plant Pathology, North Carolina State University, Raleigh, NC, 27695, USA.
Buck Institute for Research on Aging, Novato, CA, 94945, USA.
Department of Biosciences and Bioengineering, Centre for Energy, Indian Institute of Technology Guwahati, Assam 781039, India.
Department of Bioengineering, National Institute of Technology Agartala, Tripura 799046, India.
Centre for Research in Nanotechnology & Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
DBT PAN IIT Centre for Bioenergy, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Oleaginous microalga Chlorella is a promising microbial cell factory for producing lipids, transesterifiable to biodiesel, and phytochemical, high-value molecules (HVMs). To better understand the stress-induced oleaginous mechanism of Chlorella sp. FC2 IITG that closely matches with Chlorella sorokiniana based on 18s rRNA gene sequence, we performed 'Algomics' by systematically integrating metabolomics and proteomics data in response to time-resolved nitrogen-limitation: 40 h (mild), 88 h (moderate), and 120 h (severe). Ten HVMs belonging to four biological classes: triacylglycerol (TAG), polyunsaturated fatty acids (PUFA), phytosterols, and terpenoids were annotated using untargeted metabolomics and MS/MS fragmentation pattern match to the spectral library. In particular, the study evidenced 4× and 6× increased accumulation of two different PUFA: 9(S)HpOTrE and dihomo-gamma-linolenic acid, respectively, in nitrogen-limitation conditions. Co-extraction of TAG and PUFA could lower the biodiesel production cost for feasible commercialization. The investigation found a maximum accumulation of TAG 59:10 at 40 h, while that for TAG 54:4 was recorded at 88 h, which suggests different TAG species could be induced by regulating nitrogen-limitation severity. Elevated ꞵ-oxidation, glycolysis, and tricarboxylic acid (TCA) cycle identified in proteomics analysis could provide the substrates, phosphoenolpyruvate, pyruvate, and acetyl CoA, for different phytochemical accumulation in response to nitrogen limitation. The multiomics data unraveled a metabolic tug-of-war ongoing between biomass and storage lipid (TAG) accumulation during nitrogen-limitation, which involved multiple processes including hindered CO2 fixation, the supply of energy, reductants, and carbon reallocation from proteins and membrane lipids. These ﬁndings provide distinct oleaginous mechanisms in non-model microalgae, Chlorella sp. FC2 IITG, and engineerable targets for microalgal trait improvements.
- 'Algomics' of non-model nitrogen-limited microalgae to realize metabolic tug-of-war for biomass and TAG assimilation.
- MS/MS annotation reveals accumulation of phytochemicals: TAGs, PUFAs, phytosterols, and terpenoids.
- 4× and 6× increase of two different PUFAs: 9(S)HpOTrE and dihomo-gamma-linolenic acid, respectively, during nitrogen-limitation.
- Severity modulation of nitrogen-limitation results in varied TAG species.
- Biorefining TAG and PUFA for economic feasibility in large-scale biodiesel production.