Abstract
Most marine bacteria can produce exopolysaccharides (EPS). However, very few structures of EPS produced by marine bacteria have been determined. The characterization of EPS structure is important for the elucidation of their biological functions and ecological roles. In this study, the structure of EPS produced by a marine bacterium, Alteromonas sp. JL2810, was characterized, and the biosorption of the EPS for heavy metals Cu2+, Ni2+, and Cr6+ was also investigated. Nuclear magnetic resonance (NMR) analysis indicated that the JL2810 EPS have a novel structure consisting of the repeating unit of [-3)-α-Rhap-(1→3)-α-Manp-(1→4)-α-3OAc-GalAp-(1→]. The biosorption of the EPS for heavy metals was affected by a medium pH; the maximum biosorption capacities for Cu2+ and Ni2+ were 140.8 ± 8.2 mg/g and 226.3 ± 3.3 mg/g at pH 5.0; however, for Cr6+ it was 215.2 ± 5.1 mg/g at pH 5.5. Infrared spectrometry analysis demonstrated that the groups of O-H, C=O, and C-O-C were the main function groups for the adsorption of JL2810 EPS with the heavy metals. The adsorption equilibrium of JL2810 EPS for Ni2+ was further analyzed, and the equilibrium data could be better represented by the Langmuir isotherm model. The novel EPS could be potentially used in industrial applications as a novel bio-resource for the removal of heavy metals.
Highlights
Exopolysaccharides (EPS) are high-molecular weight polymers consisting mainly of carbohydrates
The EPS produced by JL2810 had a high molecular weight (>1.67 × 105 ) and contained large amounts of galacturonic acid (GalA) [32]
These results suggested that the biosorption of EPS with heavy metals is selective, which depends on the structure and functional groups of the adsorbent as well as the state, size, and bond depends on the structure and functional groups of the adsorbent as well as the state, size, and bond energy of metal ions [22]
Summary
Exopolysaccharides (EPS) are high-molecular weight polymers consisting mainly of carbohydrates. Until now very few EPS structures produced by marine bacteria have been determined [2], and the characterization of EPS structures is important for the elucidation of their biological functions and ecological roles. Several methods have been developed to remove heavy metal ions from aqueous solutions such as ion-exchange, reverse osmosis, filtration, precipitation, coagulation, and biosorption [19]. Among these methods, biosorption is regarded as one of the most promising technologies due to its advantages of low cost, short operation time, and the reusability of biomaterials [20]. The structure of JL2810 EPS was determined and the biosorption of the EPS for heavy metals of Cu2+ , Ni2+ , and Cr6+ was investigated
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