# Biosorption of Heavy Metals by the Bacterial Exopolysaccharideaccharide FucoPol
## 3 Results and Discussion
### Evaluation of the Metal-Binding Ability of FucoPol  
The metal-binding efficiency of FucoPol was tested by incubating FucoPol for 24 h in solutions containing 10 mg/L of Pb\({}^{2+}\), Cu\({}^{2+}\), Zn\({}^{2+}\) or Co\({}^{2+}\). The resulting metal removal efficiency (\(M\)) and metal uptake (\(q\)) values are presented in Figure 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Organism** & **Sugar Composition** & **Non-Sugar Residues** & **M\({}_{\mathbf{w}}\)** & **Bisorption Capacity** & **References** \\  & **(wt\% or Molar Ratio)** & **(wt\%)** & **(Da)** & **(mg/gEPS or \%)** & **References** \\ \hline _Alternomonas mackeddii subsp_ & Glc, Glc, Gal, Man and GalA & Protein (4 \%) & n.a. & \(\text{Pb}^{2+}\): 316 & [33] \\ _fitiensis_ & (2.4:1.6:1.4:1.1:1.1:0) & Protein (4 \%) & n.a. & \(\text{Zn}^{2+}\): 75 & [33] \\  & Circ, Frua, Man, Gal & & & \(\text{Pb}^{2+}\): 1103 or 98.3\% & \\ _Bacillus firms_ MS-102 & (12.1:5.7:3.1:1.0) & Pyr (6.3 \%) & n.a. & \(\text{Cu}^{2+}\): 860 or 74.9\% & [21] \\  & Uronic acids (38 \%) & & & \(\text{Zn}^{2+}\): 722 or 61.8\% & \\  & Man, Glc (1-21) & & & \\ _Bacillus_ sp, F19 & Uronic acids (37 \%) & Protein (16.4\%) & n.a. & \(\text{Cu}^{2+}\): 89.6 & [34] \\  & amino sugars (0.5 \%) & & & \(\text{Pb}^{2+}\): 108.0 or 93.9\% & \\ _Enterobacter At7_ & Fuc, Gal, Glc and GlcA & Protein (10.8\%) & \(4.4\times 10^{6}\) & \(\text{Cu}^{2+}\): 23.5 or 36.1\% & This study \\  & (2.0:1.9:0.9:0.5) & Ac, Pyr, Succ (12.3\%) & \(\text{Zn}^{2+}\): 20.1 or 35.9\% & \\  & & & & \(\text{Co}^{2+}\): 20.3 or 32.7\% & \\ _Methylobacterium organophilum_ & Gal, Man, Glu (32:2) & Protein (6.1\%) & & \(\text{Pb}^{2+}\): 1842 & \\  & Uronic acids (12.4\%) & Pyr (5.1\%) & n.a. & \(\text{Cu}^{2+}\): 200.3 & [35] \\  & Glc, Man, Gal, Fuc, Rha & & & \(\text{Pb}^{2+}\): 303.0 & \\  & (54.6, 25.6, 12.9, 3.8, 3.1\%) & Pyr (8.7\%) & n.a. & \(\text{Cu}^{2+}\): 12.3 & [20] \\  & Uronic acids (28.3\%) & Acetyls (4.13\%) & & & \(\text{Co}^{2+}\): 78.8 & [20] \\  & Aminusogars (2.8\%) & - & n.a. & \(\text{Co}^{2+}\): 20.5 & \\  & & - & n.a. & \(\text{Pb}^{2+}\): 277.5 & [23] \\  & Neutral sugars (30.6\%) & & & \(\text{Pb}^{2+}\): 79.7\% & \\  & Uronic acids (2.35\%) & & & \(\text{Cu}^{2+}\): 87.4\% & [36] \\  & Aminusogars (0.78\%) & & & \(\text{Zn}^{2+}\): 80.6\% & \\  & & & & \(\text{Po}^{2+}\): 215.6 & \\  & & & & \(\text{Co}^{2+}\): 14 & \\  & & & & \(\text{Co}^{2+}\): 14 & \\  & & & & \(\text{Po}^{2+}\): 189.3 & [88] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Microbial EFS with biosorption capacity towards heavy metals (Man, mannose; Glc, glucose; Gal, galactose; Rha; rhamnose; Fuc, fucose: Fru, fructose; GlcA, glucuronic acid; GaIA, galacturonic acid; Pyr, pyruvate; Succ, succinate; Ac, acetate). FucoPol was able to adsorb all the tested metal species, although with different degrees of efficiency. Considering the overall metal removal efficiency, \(M\), FucoPol had a higher affinity for Pb\({}^{2+}\), since \(93.9\pm 5.3\%\) of Pb\({}^{2+}\) was removed from the solution. For the remaining tested cations, Cu\({}^{2+}\), Zn\({}^{2+}\) and Co\({}^{2+}\), considerably lower values were obtained for \(36.1\pm 1.1\%\), \(35.9\pm 3.4\%\) and \(32.7\pm 2.1\%\), respectively (Figure 1). Considering the results, under the tested conditions, the preferential metal adsorption was Pb >> Cu > Zn > Co. When considering the overall specific metal uptake, Pb\({}^{2+}\) also presented the highest value, \(41.1\pm 2.3\) mg/g, while Co\({}^{2+}\), Zn\({}^{2+}\) and Cu\({}^{2+}\) had considerably lower \(q\) values of \(23.5\pm 0.7\) mg/gEPS, \(20.1\pm 1.4\) mg/gEPS, and \(20.3\pm 1.0\) mg/gEPS, respectively (Figure 1). The different removal efficiency observed for Pb\({}^{2+}\) in comparison with Co\({}^{2+}\), Zn\({}^{2+}\) and Cu\({}^{2+}\) might be attributed to the different charge density of the ions, which is dependent on the cations ionic size [21].