Background: Biofuels produced from trans-esterification of high lipid
content in microalgae represent a promising alternative renewable source of energy
to the limited and depleted global fossil fuel reservoir. The most critical step in
such a process is the harvesting of algal cells.
Objective: We aimed to improve the current methodology for microalgae harvesting
via utilizing biosynthesized silver nanoparticles (AgNPs) from Synechocystis sp.
ElfSCS31 as an eco-friendly, stable, and affordable flocculant agent.
Methods: AgNPs were prepared by the green synthesis method using the alcoholic
extract of Synechocystis sp. ElfSCS31. The synthesized nanoparticles were
characterized by Zeta sizer, X-ray Diffraction (XRD), Fourier Transform Infrared
Spectroscopy (FT-IR), and UV-Vis Spectroscopy. Biosynthesised AgNPs were
applied for harvesting 20 microalgae strains, and then, harvesting efficiency was
determined by UV Spectrophotometry.
Results: Our results revealed an average size of polydispersed nanoparticles
ranging from 10 to 100 nm for prepared AgNPs and the potential of 1.78 mV, with
an average crystallite size of 22 nm. Biosynthesised AgNPs exhibited harvesting
efficiency towards different strains of microalgae, which reached 97% in some
strains as in Chlorella lobophora and Chlorococcum oleofaciens.
Conclusion: The presented study introduces a feasible strategy using biosynthesized
AgNPs as a flocculant agent to harvest different strains of microalgae at normal
growth conditions of light and temperature. Our developed method could replace the
classical high-cost step of harvesting that leads to unravelling the full potential of
microalgae as a promising and fascinating source for biofuels production.