The trafficking of HgII by alleviating its toxicity via Citrobacter sp. IITISM25 in batch and pilot-scale investigation

The study aims to see how effective the Citrobacter species strain is in removing HgII under stressful conditions. For this, a response surface methodology was chosen to optimized pH, temperature, and biomass for effective biotransformation of HgII. The optimized value for pH, temperature, and biomass were 6.5, 30 °C, and 2 mg/l with 89% HgII removal potential. TEM-EDX showed accumulated mercury onto the bacterial surface. Pot study was conducted to check the potentiality of this strain in alleviating the toxicity in Solanum lycopersicum L. under different concentrations of mercury. The enhancement in antioxidative enzymes, as well as mercury accumulation, was observed in test plants inoculated with IITISM25. Obtained result showed a greater accumulation of mercury in the root system than that of the shoot system due to poor translocation. Moreover, mercury reductase enzyme synthesis was also boosted by the addition of β-mercaptoethanol and L-cysteine. The optimized condition for maximum enzyme synthesis was at pH 7.5 and temperature 30 °C with Km = 48.07 μmol and Vmax = 9.75 μmol/min. Thus, we can say that Citrobacter species strain IITISM25 can be effectively applied in remediation of HgII stress condition as well as promotion of Solanum lycopersicum L growth under stress conditions as a promising host. [Display omitted] •Citrobacter sp. a novel bacterial strain, isolated from the mercury contaminated soil.•Bioaccumulation, biosorption and biovolatilization responsible for the biotransformation of HgII with removal of 21–89%.•Presence of merA gene confirms the volatilization of HgII to Hg0.•Characterization of strain was done by SEM, TEM-EDX, XRD, XPS and FTIR.•Citrobacter sp. stimulated the growth and antioxidative enzyme in Solanum lycopersicum under Hg stress.