Performance evaluation of different harvesting methods and cultivation media on the harvesting efficiency of microalga and their fatty acids profile

Abstract Harvesting techniques directly affect the quality and quantity of microalgal biomass as well as the total cost of final products. In this study, the harvesting efficiency of freshwater microalga, Scenedesmus quadricauda, from synthetic medium (Bold's Basal Medium, BBM) and real wastewater (dairy wastewater, DWW) was studied using ferric chloride (FeCl3). For this purpose, the effects of three variables namely solution pHs (3, 7, and 11), coagulant concentrations (100, 400, and 700 mg/L), and reaction times (5, 10 and, 15 min) on the harvesting efficiency of microalgae were evaluated. The highest harvesting efficiencies from BBM and DWW media were achieved as 95.75% (pH 11, 700 mg/L coagulant concentration, and 10 min reaction time) and 87.11% (pH 7, 700 mg/L coagulant concentration, and 15 min reaction time). The harvested microalgal biomasses were subsequently used for the lipid extraction. The analysis of lipids profile showed that the cultivation media (BBM and DWW), harvesting methods (coagulation and centrifugation), and biomass storage time (one day and two months) significantly affected the percentages of saturated fatty acids (SFAs) and poly unsaturated fatty acids (PUFAs) in microalgal lipids. The findings of this study revealed that the harvesting methods and cultivation media are two major factors that remarkably influenced the harvesting efficiency of microalga and the fatty acids of microalgal lipids as well.