Screening and Characterization of Microbially Produced Iron Binding Exobiopolymers

Abstract

Human activities release large amounts of toxic elements such as iron in nature which can be harmful to human beings. Exobiopolymers can act as substitutes to other technologies for iron removal as they are more economical, effective and safe alternative to conventional processes. In the present study, removal of iron by exobiopolymers was investigated. Firstly, screening of iron binding by exobiopolymers extracted from eighteen different isolates was evaluated. Out of eighteen different exobiopolymers, five exobiopolymers viz. W1b, P2, Z3, X2 and W2b with high iron binding ability were selected for further studies. Characterization studies showed that the chemical composition of exobiopolymer consisted of sugars, proteins, uronic acids and amino sugars. SEM demonstrated the morphological changes of the exobiopolymers by the binding of metallic cations and EDS spectrum revealed the percentage weight of components present before and after iron binding by exobiopolymers. FTIR analysis indicated the presence of carboxyl, esters, hydroxyl, and sulphate groups of exobiopolymers involved in the metal binding processes. The explaination for adsorption of iron by exobiopolymers is the interaction between metal cations and negatively charged acidic functional groups present on exobiopolymers structure. Optimization studies revealed that the optimal binding efficiency was observed at optimum iron concentration and exobiopolymer concentration of 20 ppm and 5 ppm, respectively, in the case of P2, Z3, X2, W2b and iron concentration of 5 ppm in case of W1b. The optimized results were studied mathematically by Langmuir and Freundlich adsorption isotherms and the parameters were estimated using MATLab computational tool. The maximum adsorption capacities calculated according to isotherms were 3500 mgg-1, 3240 mgg-1, 3220 mgg-1, 3500 mgg-1 and 2440 mgg- 1 of exobiopolymers P2, Z3, X2, W2b and W1b, respectively. This finding could be the powerful step in the development of a low cost biological adsorbent i.e. exobiopolymers in bioremediation process.