Abstract
Biological treatments to degrade cyanide are a powerful technology for cyanide removal from industrial wastewaters. It has been previously demonstrated that the alkaliphilic bacterium Pseudomonas pseudoalcaligenes CECT5344 is able to use free cyanide and several metal−cyanide complexes as the sole nitrogen source. In this work, the strain CECT5344 has been used for detoxification of the different chemical forms of cyanide that are present in alkaline wastewaters from the jewelry industry. This liquid residue also contains large concentrations of metals like iron, copper and zinc, making this wastewater even more toxic. To elucidate the molecular mechanisms involved in the bioremediation process, a quantitative proteomic analysis by LC-MS/MS has been carried out in P. pseudoalcaligenes CECT5344 cells grown with the jewelry residue as sole nitrogen source. Different proteins related to cyanide and cyanate assimilation, as well as other proteins involved in transport and resistance to metals were induced by the cyanide-containing jewelry residue. GntR-like regulatory proteins were also induced by this industrial residue and mutational analysis revealed that GntR-like regulatory proteins may play a role in the regulation of cyanide assimilation in P. pseudoalcaligenes CECT5344. The strain CECT5344 has been used in a batch reactor to remove at pH 9 the different forms of cyanide present in industrial wastewaters from the jewelry industry (0.3 g/L, ca. 12 mM total cyanide, including both free cyanide and metal−cyanide complexes). This is the first report describing the biological removal at alkaline pH of such as elevated concentration of cyanide present in a heterogeneous mixture from an industrial source.
Highlights
Several billion liters of liquid wastes containing cyanides are produced at large scale by industrial activities such as mining and metal processing, electroplating, goal coking and nitrile polymers synthesis [1]
Pseudomonas pseudoalcaligenes proteome in biodegradation of jewelry cyanide-containing residues design, data collection and analysis, decision to publish, or preparation of the manuscript
Pseudomonas pseudoalcaligenes proteome in biodegradation of jewelry cyanide-containing residues different transport systems have been described
Summary
Several billion liters of liquid wastes containing cyanides are produced at large scale by industrial activities such as mining and metal processing, electroplating, goal coking and nitrile polymers synthesis [1]. Cyanide-containing wastewaters often contain heavy metals and metalloids that increase their toxicity, making them hazardous effluents difficult to remove from the environment. In these wastewaters cyanide is often found as free ion (CN−) as well as metal−cyanide complexes [1]. 1.5 M), including free cyanide (CN− in dissolution) and both weak and strong metal–cyanide complexes [2,3,4] These effluents must not be discharged without decreasing cyanide concentrations to levels lower than 1 mg/L. Economic and environmental considerations make biological technologies useful in the removal of cyanide from industrial wastewaters, and several biological treatments have been described for detoxification of free cyanide and some metal–cyanide complexes present in mining wastewaters [7,8,9]
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