Cleanup of industrial effluents containing heavy metals : a new opportunity of valorising the biomass produced by brewing industry

Heavy metal pollution is a matter of concern in industrialised countries. Contrary to organic pollutants, heavy metals are not metabolically degraded. This fact has two main consequences: its bioremediation requires another strategy and heavy metals can be indefinitely recycled. Yeast cells of Saccharomyces cerevisiae are produced at high amounts as a by-product of brewing industry constituting a cheap raw material. In the present work, the possibility of valorising this type of biomass in the bioremediation of real industrial effluents containing heavy metals is reviewed. Given the auto-aggregation capacity (flocculation) of brewing yeast cells, a fast and off-cost yeast separation is achieved after the treatment of metal-laden effluent, which reduces the costs associated with the process. This is a critical issue when we are looking for an effective, eco-friendly, and low-cost technology. The possibility of the bioremediation of industrial effluents linked with the selective recovery of metals, in a strategy of simultaneous minimisation of environmental hazard of industrial wastes with financial benefits from reselling or recycling the metals, is discussed

Impact of multi-metals (Cd, Pb and Zn) exposure on the physiology of the yeast Pichia kudriavzevii

Metal contamination of the environment is frequently associated to the presence of two or more metals. This work aimed to study the impact of a mixture of metals (Cd, Pb and Zn) on the physiology of the non-conventional yeast Pichia kudriavzevii. The incubation of yeast cells with 5 mg/l Cd, 10 mg/l Pb and 5 mg/l Zn, for 6 h, induced a loss of metabolic activity (assessed by FUN-1 staining) and proliferation capacity (evaluated by a clonogenic assay), with a small loss of membrane integrity (measured by trypan blue exclusion assay). The staining of yeast cells with calcofluor white revealed that no modification of chitin deposition pattern occurred during the exposure to metal mixture. Extending for 24 h, the exposure of yeast cells to metal mixture provoked a loss of membrane integrity, which was accompanied by the leakage of intracellular components. A marked loss of the metabolic activity and the loss of proliferation capacity were also observed. The analysis of the impact of a single metal has shown that, under the conditions studied, Pb was the metal responsible for the toxic effect observed in the metal mixture. Intracellular accumulation of Pb seems to be correlated with the metals toxic effects observed.The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the Project "BioInd-Biotechnology and Bioengineering for improved Industrial and Agro-Food processes" (NORTE-07-0124-FEDER-000028), Co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDER. Manuela D. Machado gratefully acknowledges the post-doctoral grant from FCT (SFRH/BPD/72816/2010). Vanessa A. Mesquita gratefully acknowledges the grant from Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES). The authors also thank to Doctor Rosane Freitas Schwan to offer the yeast strain and to Doctor Helena M.V.M. Soares, from the Faculty of Engineering of Porto University, for the use of analytical facilities (AAS with flame atomization and AAS with electrothermal atomization)

Organic and inorganic mercurials have distinct effects on cellular thiols, metal homeostasis, and Fe-binding proteins in Escherichia coli

The protean chemical properties of the toxic metal mercury (Hg) have made it attractive in diverse applications since antiquity. However, growing public concern has led to an international agreement to decrease its impact on health and the environment. During a recent proteomics study of acute Hg exposure in E. coli, we also examined the effects of inorganic and organic Hg compounds on thiol and metal homeostases. On brief exposure, lower concentrations of divalent inorganic mercury Hg(II) blocked bulk cellular thiols and protein-associated thiols more completely than higher concentrations of monovalent organomercurials, phenylmercuric acetate (PMA) and merthiolate (MT). Cells bound Hg(II) and PMA in excess of their available thiol ligands; X-ray absorption spectroscopy indicated nitrogens as likely additional ligands. The mercurials released protein-bound iron (Fe) more effectively than common organic oxidants and all disturbed the Na(+)/K(+) electrolyte balance, but none provoked efflux of six essential transition metals including Fe. PMA and MT made stable cysteine monothiol adducts in many Fe-binding proteins, but stable Hg(II) adducts were only seen in CysXxx(n)Cys peptides. We conclude that on acute exposure: (a) the distinct effects of mercurials on thiol and Fe homeostases reflected their different uptake and valences; (b) their similar effects on essential metal and electrolyte homeostases reflected the energy dependence of these processes; and (c) peptide phenylmercury-adducts were more stable or detectable in mass spectrometry than Hg(II)-adducts. These first in vivo observations in a well-defined model organism reveal differences upon acute exposure to inorganic and organic mercurials that may underlie their distinct toxicology

The synthesis, crystal and molecular structures of two saccharinate-metal complexes with dipyridylamine (dipyr) as a co-ligand

The complexes [Cd(dipyr)2(sac)(H2O)] sac·H2O 1 and [Hg(dipyr)(sac)2] 2, where dipyr = dipyridylamine and sac = saccharinate, have been synthesised, and fully characterised by single-crystal X-ray diffraction at 120 K. The geometry around Cd in 1 is approximately octahedral, with the metal coordinated by two bidentate dipyr ligands, one N-bonded sac and one H2O molecule; the second sac forms the counter-ion, and there is also a water of crystallisation. An extensive H-bonded network is formed. In the anhydrous Hg complex 2, the metal has approximately tetrahedral geometry, with coordination from a bidentate dipyr ligand and two N-bonded sac groups. H-bonding interactions are again extensive, even without the presence of H2O molecules in the structure, leading to chains along the a-axis. © 2009 Elsevier B.V. All rights reserved

Mechano-synthesis of AgSrFeO₃ catalyst for epoxidation of ethylene in chemical looping set-up

Acknowledgements: Financial assistance provided by the UK Research and Innovation Grant No. EP/V048414/1 and the Botswana Institute for Technology, Research and Innovation (BITRI) under COA 001 is gratefully acknowledged.The catalyst, AgSrFeO3(imp), used in chemicals looping epoxidation of ethylene-to-ethylene oxide (EtO), is usually synthesised by a conventional impregnation method. We have used a mechano-chemical method to synthesise the catalyst,...</jats:p

Desulfurization of Morupule Coal with Subcritical Aqueous Ethanol Extraction

Coal combustion greatly contributes to global emissions of toxic gases into the atmosphere, with sulfur emissions as one of the prominent pollutants in addition to carbon dioxide. Nevertheless, Botswana utilizes Morupule's sub-bituminous coal with average sulfur and ash contents, as determined in this study being 1.9 and 24.4 % by weight with an average calorific value of 22 MJ Kg−1 to generate electricity. We report an optimized extraction method for reducing total sulfur in Morupule coal from 1.9±0.2 to 0.43±0.02 wt.% at optimum conditions of ethanol/water (90/10, v/v %) at 129 °C (105 bars) in 10 minutes. A Box–Behnken experimental design was employed to select the optimal conditions of temperature (100–180 °C), water proportion in ethanol (10–90, v/v %) and extraction time (10–30 minutes), thus reducing the total sulfur under these mild conditions compared to conventional extraction. The optimized conditions were however not efficient in removing ash