Statistical optimisation of esterase from Salinicoccus roseus strain RF1H and its potential application in synthetic dye decolorisation

Abstract

Halophilic bacteria isolated from Indian Sundarban Wetland, identified as Salinicoccus roseus strain RF1H, were screened for extracellular esterase production. Media components for esterase production under submerged fermentation were optimised using Plackett–Burman Design followed by Box-Behnken Design of Response Surface Methodology (RSM) at pH 4.0, 3.5 g/L of MgSO4, and tributyrin concentration of 1(%v/v). The regression model was significant with a determination coefficient (R 2) value of 0.826. Using RSM, the experimental value of maximum enzyme activity (2.442 UmL−1) was 1.35 fold increased. The kinetic parameters K m and V max for hydrolysis of p-nitrophenyl acetate were 9.98 mM and 2.26 µmol/min/mg respectively, establishing a high affinity for the substrate. Further, the enzyme conferred promising results in decolorisation of synthetic dyes -Malachite Green, Congo Red, Brilliant Yellow, and Orange G. Molecular docking was used to investigate the binding pockets of the esterase, enzyme-ligand interactions, and amino acids which played a key role in dye decolorisation. Docking score results and decolorisation percentage were found in good agreement. This is the first report on the biotransformation of synthetic dyes to non-toxic products using esterase from Salinicoccus roseus.