Effect of iron oxide nanoparticles on growth and biofuel potential of Chlorella spp.

Effect of iron oxide (α-Fe2O3) nanoparticles (IONPs) on microalgal growth and biofuel productivity was tested in BG11 media. IONPs supplementation produced a contradicting effect between the two species, namely, Chlorella pyrenoidosa and Chlorella sorokiniana. IONPs at 20 mg·L−1 showed up to 33.75% enhancement in biomass concentration during 15 d cultivation of C. pyrenoidosa. Conversely, the IONPs, even at a low dose of 2 mg·L−1, showed toxicity to C. sorokiniana. The highest biomass production of 2.16 g·L−1 (lipid content of 13.77 wt%) was observed at IONPs 20 mg·L−1, while 30 mg·L−1 resulted in highest lipid accumulation of 16.89 wt% (biomass concentration of 2.01 g·L−1) in C. pyrenoidosa. The variation in biomass concentration and lipid accumulation follows closely the chlorophyll-a profile, indicating the effective response to the IONPs. Scanning electron microscope images revealed nanoparticle agglomeration on the surface of C. pyrenoidosa beyond 20 mg·ed. C. pyrenoidosa was found promising for biofuel production with biofuel productivity of 20.62 TOE·ha−1·y−1 at IONPs concentration of 30 mg·L−1. Current findings reveal the feasibility of IONPs supplementation in the microalgal media to improve the growth as well as lipid content. In nutshell, the results put forward a stepping stone for the sustainable biofuel recovery from microalgal biomass in near future.