Decolorization of Textile Dye by Halophilic <i>Exiguobacterium</i> sp.VK1: Biomass and Exopolysaccharide (EPS) Enhancement for Bioremediation of Malachite Green

Abstract

Abstract The salt pan soil screened for the exopolysaccharides (EPS ) producing organisms for the decolourization textile dyes. The isolate was characterized and confirmed as Exiguobacterium sp. VK1 by 16S rRNA analysis. The enhanced production of EPS was obtained with the minimal medium which was supplemented with various carbon sources, and cassava peel which has shown a 5.9 fold increase in the EPS (7704.71 mg/L) production. Exiguobacterium sp. VK1 removed Malachite Green (MG) dye (684.38 mg/g) with the maximum biosorption capacity of 79.1% at pH 6 and 40°C. With the increased EPS production, by supplementing the cassava peel, the MG dye adsorption also increased up to 97.61%, when decolorized within 30 min by Exiguobacterium sp. VK1. It was found that Pseudo Second‐order kinetics and Freundlich isotherm is the best fit for the equilibrium adsorption process of MG dye by Exiguobacterium sp. VK1. The thermodynamic properties such as activation energy (12.993 kJ/mol), change in enthalpy (10.501 kJ/mol), change in entropy ‐254.07 J/(mol K) and change in Gibbs energy (84.945‐90.026 kJ / mol) were investigated by Arrhenius and Eyring equation using Pseudo‐second‐order kinetic model. The result revealed that the adsorption process was thermodynamically feasible.