Improvement on lipid production by Scenedesmus obliquus triggered by low dose exposure to nanoparticles.

Carbon nanotubes (CNTs), α-Fe2 O3 nanoparticles (nano Fe2 O3 ) and MgO nanoparticles (nano MgO) were evaluated for the effects on algae growth and lipid production. Nano Fe2 O3 promoted cell growth in the range of 0-20 mg·L-1 . CNTs, nano Fe2 O3 and nano MgO inhibited cell growth of Scenedesmus obliquus at 10, 40 and 0.8 mg·L-1 respectively. Neutral lipid and total lipid content increased with the increasing concentration of all tested nanoparticles. The maximum lipid productivity of cultures exposed to CNTs, nano Fe2 O3 and nano MgO was observed at 5 mg·L-1 , 5 mg·L-1 and 40 mg·L-1 , with the improvement by 8.9%, 39.6% and 18.5%. High dose exposure to nanoparticles limited increase in lipid productivity, possibly due to the repression on cell growth caused by nanoparticles-catalyzed reactive oxygen species (ROS) generation, finally leading to reduction in biomass and lipid production. Reduced accumulation of fatty acids of C18:3n3, C18:3n6 and C20:2 was observed in cells exposed to nanoparticles.