Characterization of extracellular polysaccharide/protein contents during the adsorption of Cd(II) by Synechocystis sp. PCC6803

Abstract

Cyanobacteria have been proven to be cheaper and more effective for the removal of metallic elements in aqueous solutions. In this study, the living cyanobacteria Synechocystis sp. PCC6803 was used to adsorb Cd(II) and its extracellular polymeric substances (EPS) were investigated in the adsorption process. The initial stage of adsorption of Cd(II) was a rapid process, and then increase slowly accompanied with the increases of biomass. The final adsorption percentage could achieve 86% when the Cd(II) concentration was 0.5 mg/L. It proved that Synechocystis sp. PCC6803 has a good adsorption capacity for heavy metal ions. EPS was extracted to investigate the secretion of which was dynamic and the maximum extracellular polysaccharides and proteins were 134.2 and 100.9 mg/g, respectively. Furthermore, the real-time PCR (RT-PCR) results of genes (slr0977 and exoD) involved in EPS synthesis and secretion indicated that the EPS production was firstly increased and then decreased slightly. Transmission electron microscope (TEM) observation revealed that heavy metal ions were absorbed into EPS layer. Fourier transform infrared spectrum (FT-IR) analysis showed that EPS was rich in functional groups which could combine with heavy metal ions, such as -OH and -NH groups. All the results obtained show that the secretion of EPS by cyanobacteria was one of the ways to resist heavy metal stress. And it shows a trend of rising first and then decreasing, the change regulation of which was consistent with adsorptive behavior.

Behavior and Mechanism of Cesium Biosorption from Aqueous Solution by Living Synechococcus PCC7002

“…This effect is attributed to the abundant functional groups of EPS, which include hydroxy, carboxyl, phosphoric amine, and hydroxyl groups and promote the formation of metal ion clusters [48]. Furthermore, the EPS of cyanobacteria show stronger binding capacity for metal ions than EPS from other bacteria due to the complex EPS composition and abundance of negatively charged functional groups (e.g., ester-linked acetyl groups and peptide moieties and sulfate groups [26]). Recently, EEM fluorescence spectroscopy has been applied to investigate the structural and compositional variations in EPS before and after loading with heavy metal ions, including zinc and copper [49].…”

“…EPS was extracted using a modified heating procedure that was shown to have low cell lysis and high extraction efficiency [26]. All EPS fractions were filtered through 0.45-µm cellulose acetate membranes to obtain pure EPS.…”

Variation in Extracellular Polymeric Substances from Enterobacter sp. and Their Pb2+ Adsorption Behaviors

“… 17 In addition, changes in the composition, functional group content, and surface microstructure of EPS will affect the adsorption of HMs by EPS; among these factors, the composition of EPS determines the type and content of functional groups, thereby determining the HM binding sites and amount of HM adsorbed. 18 Cai et al 19 investigated the LB-EPS and TB-EPS produced by the strain Aeromonas veronii N8 upon Zn 2+ stimulation. These two types of EPS contained different proportions of polysaccharides and proteins, and thus, their adsorption mechanisms differed.…”

Comparison of EPS Extraction Efficiences from Spirogyra fluviatilis by Chemical and Physical Extraction Methods

“…In addition, EPS also improves the process of heavy metal and radio nuclides contaminated water by enhancing the water retention capacity of the soil [9], [10]. The demands for natural polymers in various industrial applications have increased lately, and therefore, novel algae have been used to synthesize high value products, such as products of high aggregated value such as pigments, osmoprotectant, metabolites, fatty acids and proteins, may also be exploited for EPS as biosurfactants and/or bio-emulsifiers [11], [12].…”