Production of biodiesel and exopolysaccharides from Scenedesmus abundans cell factory in flat panel photobioreactor with autoflocculation harvesting strategy

Abstract

quotFatty acid methyl ester (FAME, biodiesel) production from microalgae has been gaining momentum in order to mitigate current energy demand but still facing major challenges such as low biomass production in open pond cultivation systems, unsuccessful closed photobioreactor (PBR) design, inappropriate media balancing under natural sunlight, inefficient harvesting technology and unsuitable transesterification process. Moreover, in order to make biodiesel economically viable, there is a need to exploit other products concomitantly apart from biodiesel and reduce downstream processing costs. Exopolysaccharides (EPS) are one of the major valuable byproducts secreted by some microalgae directly into the media. Concomitant synthesis of intracellular and extracellular product fractions in microbial cell factories would be an excellent biorefinery outlook for the researchers to reduce overall cost of their production and yield profits. Major factors that influence oleaginous microalgae growth and lipid production under natural sunlight are photobioreactor design, adequate supply of macronutrients and micronutrients, availability of sunlight intensity, CO2 supply, nitrogen starvation, mixing and mass transfer, process pH and culture temperature. Therefore, the algal biorefinery approach should focus on PBR design, media balancing for enrichment of multi-products, efficient harvesting technology for biomass recovery and desirable transesterification process for producing biodiesel. Arising from the above, the objectives of the study were formulated to develop process strategy for construction and characterization of medium scale flat panel PBR for producing biodiesel and exopolysaccharides from S. abundans. Accordingly, modulation of macronutrients and micronutrients were studied to enhance lipid content of S. abundans in single stage medium scale flat panel PBR under natural sunlight. Also, multi-objective optimization of nutrients was performed in this study to enhance biodiesel, autosedimentation of Scenedesmus abundans