Biological removal of inorganic Hg(II) as gaseous elemental Hg(0) by continuous culture of a Hg-resistant Pseudomonas putida strain FB-1

Abstract

A strain of broad-spectrum, mercury-resistant Pseudomonas putida FB1 was used to remove mercury as the gaseous element (Hg(0)) from a continuous axenic culture, fed with a synthetic medium containing 1 mg Hg l(-1) as HgCl2. Mercury determinations were performed in steady-state cultures using various culture fractions [whole culture, filtered supernatant, bacterial cells (dry wt), recovery trap liquid] in order to determine the removal efficiency at different dilution rates (from 0.1 to 3.0 day(-1)). The removal efficiency ranged from 99.2% to 99.8%, and the residual Hg was maintained below 5 μ l(-1) (the maximum allowable concentration of Hg in liquid wastes according to Italian law) at a dilution rate of 1.0 day(-1), corresponding to a Hg flux of 40 μg l(-1) h(-1). Hg accumulation by cell biomass was negligible for dilution rates under 1.0 day(-1). A progressive accumulation of Hg, both in the liquid phase and in cells, occurred at a higher dilution rate (3.0 day(-1); close to washout), corresponding to a Hg concentration of 25 μg g(-1) (dry wt). The estimated Km and Vmax for Hg reduction were 0.241 mg l(-1) and 9.5 mg g(-1) h(-1), respectively. In batch experiments maximum Hg removal occurred at the optimum growth temperature (28°C) of P. putida. The maximum recovery of Hg in the liquid trap was 78%.

Removal of Mercury from Chemical Wastewater by Microoganisms in Technical Scale

“…Here, we used the reduction of ionic mercury to water insoluble metallic mercury, which is catalyzed by mercury resistant bacteria, as the mechanism by which to remove mercury from solution. While volatilization of the reduced Hg 0 from batch microbial cultures was used by other groups (22,23), here we captured it as metallic mercury within the bioreactor. The active "mercury trap" constructed thus has the advantage of an extremely high efficiency per volume, since it is not saturated as conventional absorbers or ion-exchange resins.…”

A Rapid Electrochemical Procedure for the Detection of Hg(0) Produced by Mercuric-Reductase: Application for Monitoring Hg-resistant Bacteria Activity.

“…It exists in several physical and chemical forms whose toxic effects are well-known. − Although metallic mercury is relatively harmless, it generally undergoes complex and difficult-to-predict changes in the chemical form, due to its propensity to biological interactions . These circumstances have resulted in extensive research on the interaction between mercury and various chemical and biochemical systems, considering, especially, those processes that involve mercury bioavailability , and its microbiological transformations. − The latter processes are relevant, as they can profitably be exploited for remediation/detoxification of aquatic systems from Hg. − Microbe based remediation/detoxification of mercury is on forefront due to low cost and less health hazardous compared to physiochemical based strategies. , Microbial metal removal processes take advantage of the metal-resistance microorganisms which are usually isolated from polluted environments.…”