Role of nanoparticles on microalgal cultivation: A review

[Display omitted] •The effects of nanoparticle addition to microalgae growth were reviewed.•The addition of nanoparticles improved the growth and accumulation of intracellular compounds.•The nanoparticles enhanced CO2 absorption and light conversion to promote microalgae growth.•The toxicity of nanoparticles depends on the oxidation state, structure, concentration, and particle size. Microalgae have become one of the most promising environmentally friendly alternatives for biofuel production. Microalgal biomass can be used as feedstock for the synthesis of biofuels including biodiesel, bioethanol, bio-hydrogen, bio-methane, and syngas. However, large-scale biofuel production from microalgae has not yet met economic feasibility. One of the major limitations concerns to the biomass cultivation stage. Nanoparticles are emerging as potential alternatives for enhancing microalgae cultivation and harvesting. Nanoparticles addition in microalgal cultures can improve the yield of CO2 absorption, and enhance light conversion in the microalgae photobioreactor. However, aspects related to the characteristics and concentration of nanoparticles requires further investigation. Thus, this study presents a detailed review of the current trends and perspectives of nanoparticles applied to microalgae. The effects of nanoparticles in tailoring the microalgae metabolic pathways and its morphologic toxicity were investigated. Conducted studies revealed that the nanoparticle toxicity depends on its nature (particle size, oxidation state, crystal structure), concentration, cultivation media, and microalgae species. Also, the addition of nanoparticles significantly increased the accumulation of intracellular compound and growth. Further studies should be focused on optimizing nanoparticle concentration and synthesis methods to improve the microalgae cultivation process.