Production of EPS under Cr(VI) challenge in two indigenous bacteria isolated from a tannery effluent

Jin

J of Chemical Tech & Biotech

et al. 2017

BACKGROUND: Bioremediation of Cr(VI) to Cr(III) was considered a promising and cost-effective alternative to chemical and physical methods. However, Cr(VI) had toxic effects on microorganisms. This study focused on exploring the effects of different Cr(VI) concentrations on the performance of an anaerobic activated sludge reactor, extracellular polymeric substances (EPS) and microbial community structure. RESULTS: Anaerobic sludge reduced and immobilized 100.0 mg L −1 Cr(VI) in 24 h. When the Cr(VI) concentration was increased from 0.0 to 50.0 mg L −1 , the production of EPS was enhanced from 231.4 to 1262.9 mg g −1 VSS. With 80.0 mg L −1 Cr(VI) and 120.0 mg L −1 Cr(VI), EPS production was inhibited. Increase of Cr(VI) concentration changed the EPS components and had distinct effects on the functional groups of EPS. In addition, the increase of Cr(VI) stress reduced the abundance of most bacteria. CONCLUSION: Low Cr(VI) concentrations had no effect on COD Cr and NO 3 -N removal, while 120.0 mg L −1 Cr(VI) seriously inhibited on COD Cr , NO 3 -N and Cr(VI) removal. This was due to the toxicity and electron competition ability of Cr(VI). High Cr(VI) concentrations (80.0 and 120.0 mg L −1 ) also inhibited EPS production. Cr(VI) reduction was closely related with EPS.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of hexavalent chromium on performance, extracellular polymeric substances and microbial community structure of anaerobic activated sludge in a sequencing batch reactor

Jin

J of Chemical Tech & Biotech

et al. 2017

“…Quantity and composition of EPS have been shown to vary depending upon bacterial strains and environmental stresses 23, 28 . In anaerobic chemostat fed on glucose, exposure to excess Cr(VI) enhanced the EPS production 29 . Similarly, Cr(VI) stimulated the production of microbial EPS by the hydrogen-producing photosynthetic bacteria strain Rhodopseudomonas acidophila .…”

Section: Introductionmentioning

confidence: 99%

Characterization of Product and Potential Mechanism of Cr(VI) Reduction by Anaerobic Activated Sludge in a Sequencing Batch Reactor

Jin

et al. 2017

Sci Rep

Bioremediation of Cr(VI) and nitrate is considered as a promising and cost-effective alternative to chemical and physical methods. However, organo-Cr(III) complexes in effluent generally causes environmental concerns due to second-pollution. Here, Cr(VI) reduction and immobilization efficiencies of anaerobic activated sludge were investigated. Anaerobic activated sludge showed strong reduction ability of Cr(VI) and possessed a great potential of Cr(III) immobilization. Almost 100.0 mg l−1 Cr(VI) could be completely reduced and immobilized by anaerobic activated sludge in a sequencing batch reactor in 24 h. And most generated Cr(III) was accumulated outside of sludge cells. Extracellular polymeric substances (EPS) could bind to Cr(VI) and form EPS-Cr(VI) interaction to reduce the toxic effect of Cr(VI) and promote the Cr(VI) reduction. Protein-like and humic-like substances were responsible for binding with Cr(VI), meanwhile the process was a thermodynamically favorable binding reaction. Then Cr(VI) was reduced to Cr(III) by membrane-associated chromate reductase of sludge. Eventually, the generated Cr(III) might exist as poly-nuclear Cr(III) complexes adhered to sludge surfaces.

“…The EPS sample (2-5 mg) was mixed with KBr of IR spectroscopy grade in a smooth agate mortar. The mixture was then pressed under pressure of about 5-8 ton cm −2 for about 20-30 s [4,23]. The electrical charge on EPS was determined by electrophoresis method using dynamic light scattering in combination with an applied electric field [24].…”

Section: Characterization Of Epsmentioning

confidence: 99%

Exploration of an Extracellular Polymeric Substance from Earthworm Gut Bacterium (Bacillus licheniformis) for Bioflocculation and Heavy Metal Removal Potential

Banerjee

Sarkar

et al. 2020

Applied Sciences

The present study shows the potential of an extracellular polymeric substance (EPS) produced by Bacillus licheniformis strain KX657843 isolated from earthworm (Metaphire posthuma) gut in the sorption of Cu(II) and Zn(II) and in flocculation. After harvesting bacterial cells from sucrose supplemented denitrifying culture medium, the EPS was extracted following ethanolic extraction method. The Fourier Transform Infrared Spectroscopy (FTIR) and 1H and 13C Nuclear Magnetic Resonance (NMR) of EPS revealed its functional groups, electronegative constituents, unsaturated carbon, and carbonyl groups. The negatively charged functional groups of carbohydrates and protein moiety of the EPS endowed it with heavy metal binding capacity through electrostatic interactions. The highest flocculation activity (83%) of EPS was observed at 4 mg L−1 and pH 11. The metal sorption by EPS increased with increasing pH. At pH 8, the EPS was able to remove 86 and 81% Cu(II) and Zn(II), respectively, from a 25 mg L−1 metal solution. 94.8% of both the metals at 25 mg L−1 metal solutions were removed by EPS at EPS concentration of 100 mg L−1. From Langmuir isotherm model, the maximum sorption capacities of EPS were calculated to be 58.82 mg g−1 for Cu(II) and 52.45 mg g−1 for Zn(II). The bacterial EPS showed encouraging flocculating and metal sorption properties. The potential to remove Cu(II) and Zn(II) implies that the EPS obtained from the earthworm gut bacteria can be used as an effective agent for environmental remediation of heavy metals and in bioflocculation.