Biosorption of Cr (VI) from aqueous solution by extracellular polymeric substances (EPS) produced by Parapedobacter sp. ISTM3 strain isolated from Mawsmai cave, Meghalaya, India

• Published in: Environmental research Vol. 191; p. 110064
• Main Authors: Tyagi, Bhawna, Gupta, Bulbul, Thakur, Indu Shekhar
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.12.2020
• Subjects: Adsorption; Biosorbent; Biosorption kinetics; Exopolysacccharides; Extracellular Polymeric Substance Matrix - chemistry; Heavy metal removal; Hydrogen-Ion Concentration; India; Kinetics; Metals, Heavy - analysis; Parapedobacter sp; India; Exopolysacccharides; Biosorbent; Parapedobacter sp; Biosorption kinetics; Heavy metal removal
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2020.110064

In the current study, EPS producing strain Parapedobacter sp. ISTM3 was isolated from Mawsmai cave, Meghalaya, India. The strain ISTM3 showed enhanced EPS production (4.65 ± 0.10 g L−1) at optimized parameters, i.e., pH 8 and 3% molasses as a carbon source. The extracted EPS was structurally characterized by GC-MS, NMR, and FTIR analysis to investigate its monomer compositions, functional groups, and linkage analysis. GC-MS study confirmed the heteropolymeric nature of EPS, whereas the FTIR study confirmed the presence of an aliphatic group, amine group, uronic acid, and saccharides group in the EPS structure. Biosorption of heavy metals by EPS from an aqueous solution was investigated by using heavy metals mixture (Zn2+, Cu2+, Pb2+, Cr6+, Fe2+, and Cd2+) with 20 mg L−1 concentration of each metal. EPS showed the highest removal efficiency and metal adsorption capability for Cr6+ as compared to other heavy metals studied. Also, metal adsorption capability (19.032 mg g−1) and removal efficiency (95.10%) of Cr6+ by EPS were further increased in acidic conditions (pH 5.0). FTIR and SEM-EDX analysis confirmed the biosorption mechanism of EPS. The Freundlich and Langmuir adsorption isotherms were employed to discover the biosorption parameters for Cr6+ uptake with a concentration range of 10–200 mg L−1 by EPS (1 g L−1). The Langmuir model was found to better fit the Cr6+ adsorption by EPS having a maximum adsorption capacity of 33.783 mg g−1. With this, the present study highlights the EPS production potential of Parapedobacter sp. ISTM3, as well as the potential of extracted EPS for heavy metals removals via adsorption. •EPS producing Parapedobacter sp. ISTM3 was isolated from Mawsmai cave, India.•Bacterium produces enhanced EPS (4.65 g L−1) by utilizing molasses.•FTIR and SEM-EDX analysis confirmed the biosorption of heavy metals by EPS.•EPS showed high adsorption capacity of Cr6+ with 95.10% removal efficiency.•Freundlich and Langmuir isotherm model were employed for biosorption study.