A method for removal of toxic chromium using dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae

Abstract

A method for removal of toxic hexavalent chromium (chromate: CrO2-4) was developed by use of dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae (HO1). E. cloacae strain HO1 cells were put in dialysis (semipermeable membrane) sacs, and the sacs were submerged in water containing toxic CrO2-4. The dialysis sacs allowed CrO2-4 to diffuse into the culture, and CrO2-4 was reduced anaerobically in the dialysis sacs by the E. cloacae cells. Because reduced chromium readily formed insoluble chromium hydroxides in the dialysis sacs, the greater part of reduced chromium was unable to diffuse out through the semipermeable membrane. Thus the dialysis culture of E. cloacae strain HO1 could successfully remove toxic chromium from the surrounding water. If the initial concentration of CrO2-4 was less than 4 mM (208 ppm as chromium), about 90% of the total chromium could be removed from water by the described method.

Bioremediation of hexavalent chromium (VI) by a soil-borne bacterium,Enterobacter cloacaeB2-DHA

“…Thus, all subsequent experiments were conducted at 37°C in media with pH 7.0. These data are consistent with previously reported [13] optimum pH and temperature for Enterobacter cloacae ranging from 7.0-8.0 and 30-37°C respectively. Wang et al [43] reported that reduction of Cr(VI) by E. cloacae occurred at pH 6.5 to 8.5 and it was strongly inhibited at pH 5.0.…”

“…The strain E. cloacae B2-DHA exhibited a MIC higher than 1000 µg/mL of K2CrO4 which is an indication that this strain is resistant to very high concentrations of chromate than that reported previously by Komori et al, [13] Yamamoto et al, [14] Clark, [15] Rege et al, [16] and…”

“…This is consistent with previously reported studies on chromate reduction by Enterobacter cloacae. [13][14][15][16][42][43][44] …”

“…[11] Enterobacter aerogenes, [12] Enterobacter cloacae, [13][14][15][16] Microbacterium, [17] Desulfovibrio, [18] Escherichia coli, [19] Shewanella alga, [20] Bacillus sp. [8] and several other bacterial species.…”

Chromium Removal by Using Chosen Pseudomonads

“…But they require large quantities of chemical reagents and high amount of energy [7]. Several treat ment processes have be en s ug geste d f or th e r e mo val of h e av y met als fro m a qu eou s waste streams: adsorption, biosorption, ion exchange, chemical precip itation and electrochemical methods: electrowinning, electrodialysis, electrodeionization, memb rane-less electrostatic shielding, electrodialysis and electrocoagulation which are h ighly expensive.…”