Potential of Hydrocotyle vulgaris for phytoremediation of a textile dye: Inducing antioxidant response in roots and leaves

• Evaluation of the potential of H. vulgaris in biodegradation of a textile dye.
• Recognition of the compounds produced by biological processes involving H. vulgaris.
• Investigation of the effect of operational conditions on dye removal efficiency.
• Study of dye stress effect in inducing antioxidant enzymes in roots and leaves.
• Predicting the removal (percent) by an artificial neural network (ANN) model.

The potential of Hydrocotyle vulgaris as an aquatic plant species was evaluated for phytoremediation of C.I. Basic Red 46 (BR46) from nutrient solution. Under the optimized experimental conditions, BR46 was removed up to 95% from incubation medium by H. vulgaris. The ability of the plant in consecutive removal under long term repetitive experiments confirmed the biodegradation process. Accordingly, a number of produced intermediate compounds were identified. An artificial neural network (ANN) model was developed to predict the biodegradation efficiency. A predictive performance (R2=0.974) was obtained based on the network results. Interestingly, dye stress enhanced the activity of antioxidant enzymes including superoxide dismutase, peroxidase and catalase in H. vulgaris roots and leaves. Enzymatic responses found to be highly depended on the plant organ and dye concentration in the liquid medium. Overall, the increase in the activity of antioxidant enzymes was much higher in the roots than in the leaves. Nevertheless, no significant increase in the malondialdehyde (MDA) content was detected in both roots and leaves which reflects the high efficiency of antioxidant system in the elimination of reactive oxygen species.