Micro-Phyto-assisted reduction of Hexachlorocyclohexane (HCH) contamination in soil: A sustainable solution to mitigate HCH pollution

Abstract

This study pioneers a sustainable solution for Hexachlorocyclohexane (HCH) remediation through a unique microbe-assisted phytoremediation strategy, utilizing Ricinus communis inoculated with a novel yeast-bacteria rhizo-inoculum, Priestia megaterium and Meyerozyma caribbica. This combination achieved unprecedented reductions of its various isomeric residues viz. α-HCH (85.09%), β-HCH (91.80%), γ-HCH (95.24%), and δ-HCH (89.78%) over a 90-day pot experiment. R. communis demonstrated significant bioaccumulation of ΣHCH, primarily in its roots, followed by shoots and leaves. The HCH-exposed plants treated with mixed culture treatment exhibited a marked decrease in antioxidative defense enzyme activities: SOD (79%), APX (56%), GPX (68%), and CAT (55%) compared to control plants. Additionally, reduction of HCH residues in rhizospheric soil was significantly enhanced in the presence of microbial inoculum. Multivariate Principal Component Analysis (PCA) indicated significant differences in soil physico-chemical properties and plant enzymatic activities between treatments, closely linked to variations in HCH concentrations. PCA components accounted for 49.07% (PC1) and 15.02% (PC2) of the total variance in soil properties, and 65.66% (PC1) and 19.04% (PC2) in root enzymatic activities, with leaf enzymatic activities showing 69.70% (PC1) and 15.20% (PC2). These results suggest that inoculating R. communis with this novel yeast-bacteria mixed culture offers a highly effective and promising approach for the remediation of HCH-contaminated sites.