Evaluation of biosorption potency of Acinetobacter sp. for removal of hexavalent chromium from tannery effluent

Abstract

Two bacterial consortia were developed by continuous enrichment of microbial population of tannery and pulp and paper mill effluent contained Serratia mercascens, Pseudomonas fluorescence, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter sp. identified by 16S rDNA method. The consortia evaluated for removal of chromate [(Cr(VI)] in shake flask culture indicated pulp and paper mill consortium had more potential for removal of chromate. Acinetobacter sp. isolated from pulp and paper mill consortium removed higher amount of chromate [Cr(VI)] under aerobic conditions. Parameters optimized in different carbon, nitrogen sources, and pH, indicated maximum removal of chromate in sodium acetate (0.2%), sodium nitrate (0.1%) and pH 7 by Acinetobacter sp. Bacteria was applied in 2-l bioreactor significantly removed chromate after 3 days. The results of the study indicated removal of more than 75% chromium by Acinetobacter sp. determined by diphenylcarbazide colorimetric assay and atomic absorption spectrophotometer after 7 days. Study of microbial [Cr(VI)] removal and identification of reduction intermediates has been hindered by the lack of analytical techniques. Therefore, removal of chromium was further substantiated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) which indicated bioaccumulation of chromium in the bacterial cells.

Isolation and characterization of a chromium-resistant bacterium Serratia sp. Cr-10 from a chromate-contaminated site

“…The species in the genus had been investigated for their ability to produce cohesive biofilm supporting nanocrystalline palladium catalyst, which was then used to reduce Cr(VI) to less dangerous Cr(III) (Beadregard et al 2010); additionally, several Ser. mercascens strains were isolated from tannery effluent containing Cr(VI) (Srivastava and Thakur 2007), no Cr-resistant Serratia sp. reported expressly.…”

Bioremediation of Tannery Wastewater by Chromium Resistant Fungal Isolate Fusarium chlamydosporium SPFS2-g

“…The results indicated that some native fungi have a marked adaptation to heavy metals under constant metal stress for a long time, and the toxic metals were even used as micronutrients by these growth stimulated fungi 25 . Similar to our findings, Aspergillus niger, Aspergillus lentulus, Penicillium sp., and Fusarium solani isolated from contaminated sites have been reported to tolerate 1000 ppm Cr(VI) 17,26,27 . The tolerance to Cr(VI) occur by various mechanisms such as transport across the cell membrane, biosorption to cell walls and entrapment in extracellular capsules, precipitation, complexation and oxidation-reduction reactions 15 .…”

“…Generally, microbial biomasses have evolved various measures to respond to heavy metals stress via processes such as transport across the cell membrane, biosorption to cell walls, entrapment in extracellular capsules, as well as precipitation and transformation of metals 15 . There are some studies which have been conducted employing bacteria for remediation of components of tannery wastewater 16,17 or fungal mycelia as bioabsorbent 18,19 . But, most of the studies are pollutant specific targeting only one or two specific pollutants mostly chromium.…”

Hexavalent Chromium Reduction and Accumulation by Acinetobacter AB1 Isolated from Fez Tanneries in Morocco

“…The heavy metal can also pass into the cell across the cell membrane through the cell metabolic cycle [31]. This mode of metal uptake is referred as active uptake.…”