Synergistic dynamics of critical cofactors effectuates fuel relevant metabolic profile of Scenedesmus sp.: Targeting cleaner energy production

Abstract

Microalgae based biofuel is dictated to a great extent by certain synergistic interactions between critical nutrients as well as the quality and quantity of light energy available. For latitude regions with high light irradiance for a greater part of year, it is important to optimize the proportions of critical nutrients for microalgae species to display a suitable metabolic profile and not loose advantage when total light energy input increases. In this study, the conjunct impact of light intensity using white LED, together with photoperiod and nutrients (nitrate, phosphate and glucose) depleted and replete conditions on energy storage metabolites and fuel characteristics of Scenedesmus sp. were investigated under a mixotrophic growth regime. Results show that Scenedesmus sp. could efficiently exploit even very intense light, for longer duration (216 μmolm−2s−1 at 16:8 light: dark photoperiod) in presence of 1.5 g/L of sodium nitrate, 0.04 g/L of di-sodium hydrogen phosphate and 5 g/L of glucose (G5N1.5P0.04) to produce a biomass of 1782.4 ± 56.8 μg/mL with a specific growth rate of 0.2 ± 0.007 day−1. High light intensity (216 μmolm−2s−1) and organic carbon at 16:8 light: dark photoperiod (L16:D8) led to increased synthesis of carbohydrate content in the absence of nitrate and phosphate (1924.8 ± 128.6 μg/mg at G5N0P0), increased TFA in the absence of nitrate (59.5 μg/mg at G5N0P0.04) and high lipid content (154.1 ± 7.7 μg/mg at G5N1.5P0.04) without obliterating growth. Certain vital properties that determine the biodiesel quality were computed and compared to the parallel parameters put forth by European and American biodiesel norms. These results stand to be a baseline for sustainable algal bio-refinery and create futuristic vistas for further evaluation of Scenedesmus sp. for bio-energy applications in countries like India having tropical climate with high solar incoming radiation for a greater part of the year.