Metal removal of cyanobacterial exopolysaccharides by uronic acid content and monosaccharide composition

In the present study, chromium, cadmium and metal mixed (chromium + cadmium) removal and its association with exopolysaccharides and uronic acids production in Synechocystis sp. BASO671 were investigated. It was investigated that BASO671 showed different removal ability when exposed to each metal solely and mixed metal. EPS production by BASO671 was increased following exposure to 15 and 35 ppm Cr(VI), Cd(II) and Cr(VI) + Cd(II). Monomer composition of EPS was changed after metal treatment. Uronic acid contents of metal treated cells were higher than control cells of each isolate. Also, glucuronic acid content and galactronic acid content of EPS correlated with uronic acid contents of cells. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis confirmed that a considerable amount of metals had precipitated on the cell surface. Fourier transform infrared spectrum analysis of EPSs indicated the presence of CH and CO group, which may serve as binding sites for divalent cations.