Effect of Bismuth, Gadolinium, and Cadmium Nanoparticles on Biomass, Carotenoid, and Lipid Content of Dunaliella salina (Dunal) Teodoresco.

Dunaliella salina is an extremophytic microalga and known as an excellent source of β-carotene and eicosapentanoeic acid. Moreover, D. salina has also been used in aquaculture feeds to increase the growth rate of fish and shrimp. Hence, many studies have been involved in searching for new approaches to increase the biomass of D. salina in the aquatic farming industry. This is the first report investigating the effect of bismuth oxide (Bi2O3), gadolinium oxide (Gd2O3), and cadmium telluride (CdTe) nanoparticles (NPs) on the growth of D. salina in controlled laboratory conditions. Extensive growth curve analysis was performed along with biochemical assays to determine chlorophyll-a, carotenoid, and total lipid content of D. salina under the influence of NPs. It is revealed that the lower concentration (100 µg/ml) of Bi2O3 is favorable for D. salina growth, while higher concentrations (200 and 300 µg/ml) inhibited the cell proliferation significantly. Similarly, Bi2O3 treatment led to the increase in chlorophyll-a, carotenoid, and lipid content of microalga compared to untreated culture. Gd2O3 exerted a growth inhibitory effect on microalga for initial 15 days which is later overcome by microalga showing a drastic increase in biomass after 60 days of cultivation. However, CdTe NPs displayed minor elevation in growth rate. Interestingly, the presence of Gd2O3 NPs in culture media demonstrated the highest carotenoid and total lipid content of algal cells among all three-tested NPs. Hence, Gd2O3 NPs can be considered as a vital additive during the industrial culturing of D. salina.