Biogreen remediation of chromium-contaminated soil using Pseudomonas sp. (RPT) and neem (Azadirachta indica) oil cake

The prospective of indigenous Pseudomonas sp. (RPT) and neem oil cake for enhanced removal of chromium (Cr) from contaminated soil microcosm was explored in this study. The bacteria were isolated from Cr-contaminated soil and identified as Pseudomonas sp. based on partial 16S rDNA sequencing. The isolate RPT showed high Cr(VI) tolerance (1000mg/l) and removal rate (64.4%) in batch experiments. Transmission electron microscopy observation showed that the isolate effectively precipitated the Cr both intra- and extracellularly. Microcosm studies revealed that neem oil cake amendment (7.5% w/v) enhanced Cr(VI) removal (82%) from contaminated soil. Furthermore, soil enzyme activities were increased in the biostimulated soil. The obtained results indicated that the application of neem oil cake along with indigenous Cr(VI)-resistant bacteria could inspire the bioremediation of Cr(VI)-contaminated soil field scale.