Isolated-Microalgae Cultivation in Wastewater for Biodiesel Production

Abstract

Microalgae species with high lipid-productivity and contamination-resistance is essential for feasible large-scale biodiesel production. Five microalgae cultures (Scenedesmus rubescens, Parachlorella kessleri, Chlorella vulgaris, Chlorella sorokiniana, and Scenedesmus acuminatus) were xenically isolated from municipal wastewater treatment plant and characterized in synthetic medium BG-11. Isolated-microalgae were cultivated in weak wastewater for viability test. Result shows Scenedesmus rubescens had the highest lipid content (27.56% of biomass) and productivity (18.11 mg/l/day). Cultivation in moderate wastewater showed microbial-community change in all microalgae cultures. Six DGGE bands were identified and showed several bacteria class, i.e. Cyanobacteria, Sphingobacteriia, Cytophagia, Flavobacteriia, and Gemmatimonadetes. Later, S. rubescens was cultivated in several dilution-ratios (5, 10, 20, and 30) of strong wastewater. 5 and 10 dilution-ratios showed no signs of microalgae growth due to bacteria growth. However, S. rubescens grew better in 20 and 30, with lipid productivity in 30 was two times higher than in 20. Finally, FAME was analyzed in each cultivation experiments. Parameters for biodiesel-quality were calculated based on Pinzi’s model [126]. The result showed FAME composition could fulfill biodiesel standard EN14214, especially in cetane number, viscosity, flash point, and cold filter plugging point parameters. Keywords: microalgae, lipid productivity, microbial-community change, symbiotic relationship, FAME, dilution ratio