Abstract
Microalgae are gaining commercial interests in the areas food, feed and biofuel sector. They have intrinsic ability to harness energy from sunlight and photosynthetically valorize CO2 into various bio-based products viz., triacylglycerols (TAGs), mono/poly-unsaturated fatty acids (MUFA, PUFA), pigments etc. Microalgae have adapted to grow in various nutritional environments due to their metabolic versatility and resilience. Strategic evaluation of newly isolated strain Chlorella sp. from a residential lake was performed. The strain was investigated by varying the nutritional modes to gain insights into biomass and fatty acids production. Maximum biomass (3.59 g/L) was observed in mixotrophic condition followed by heterotrophic (1.58 g/L) and autotrophic condition (0.59 g/L). The maximum lipid yield (670 mg/g DCW) was observed in mixotrophic condition whereas maximum total lipid content (36%) was observed in heterotrophic condition. Significant correlation was noticed between fluorescence parameters measured by OJIP and non-photochemical quenching (NPQ) with the function of nutritional mode variations. Autotrophic condition showed higher photosynthetic activity which was well correlated with high fluorescence intensity as represented by OJIP, NPQ1, and NPQ2 curves. Good balance of saturated fatty acids (SFA) and unsaturated fatty acids was observed in autotrophic mode, whereas polyunsaturated fatty acids (PUFA) and mono unsaturated fatty acid (MUFA) content were relatively higher in mixotrophic and heterotrophic conditions.
Highlights
Microalgae produce commercially important biomolecules viz. proteins, carbohydrates, lipids, vitamins, pigments, and other biologically active compounds having direct applications in food and health, biofuel, pharmaceutical and cosmetic sectors (Mayfield and Golden, 2015)
The parameters that are generally used to measure the physiological state of the photosynthetic organisms are non-photochemical quenching (NPQ), quantum yield, photosynthetic efficiency (Fv/Fm), relative electron transport rate, and light saturation (Ek)
A phylogenetic tree showing the relationship among the evolutionary identical strains was constructed using the Molecular Evolutionary Genetics Analysis (MEGA) 6.0 software which is extensively used for high throughput molecular and evolutionary data anlaysis and phylogenetic tree construction (Zhang et al, 2018)
Summary
Microalgae produce commercially important biomolecules viz. proteins, carbohydrates, lipids, vitamins, pigments, and other biologically active compounds having direct applications in food and health, biofuel, pharmaceutical and cosmetic sectors (Mayfield and Golden, 2015). Heterotrophic cultivation replaces light requirement by organic carbon source and can assimilate complex carbon to produce high density biomass (Lowrey et al, 2015; Venkata Mohan et al, 2015). Mixotrophic growth is the sum of individual growths of autotrophic and heterotrophic modes and explores the advantages of both CO2 and organic carbon as energy source (Blanken et al, 2014; Chandra et al, 2014; Rohit and Venkata Mohan, 2016). The parameters that are generally used to measure the physiological state of the photosynthetic organisms are non-photochemical quenching (NPQ), quantum yield, photosynthetic efficiency (Fv/Fm), relative electron transport rate (rETR), and light saturation (Ek). Exposure to photosynthetically supersaturating light triggers the activation of energy dissipating processes that lowers the yield of chlorophyll “a” fluorescence and is generally termed as NPQ process (Masojídek et al, 1999)
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