Immobilization of E. coli expressing Bacillus pumilus CynD in three organic polymer matrices
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Cyanide is toxic to most living organisms. The toxicity of cyanide derives from its ability to inhibit the enzyme cytochrome C oxidase of the electronic transport chain. Despite its high toxicity, several industrial processes rely on the use of cyanide, and considerable amounts of industrial waste must be adequately treated before discharge. Biological treatments for the decontamination of cyanide waste include the use of microorganisms and enzymes. Regarding the use of enzymes, cyanide dihydratase (CynD), which catalyzes the conversion of cyanide into ammonia and formate, is an attractive candidate. Nevertheless, the main impediment to the effective use of this enzyme for the biodegradation of cyanide is the marked intolerance to the alkaline pH at which cyanide waste is kept. In this work, we explore the operational capabilities of whole E. coli cells overexpressing Bacillus pumilus CynD immobilized in three organic polymer matrices: chitosan, polyacrylamide, and agar. Remarkably, the immobilized cells on agar and polyacrylamide retained more than 80% activity even at pH 10 and displayed high reusability. Conversely, the cells immobilized on chitosan were not active. Finally, the suitability of the active complexes for the degradation of free cyanide from a solution derived from the gold processing industry was demonstrated.
KeywordsBioremediation Cyanide Cyanide dihydratase Immobilization Whole cells Gold mining effluents
The authors would like to thank Dr. Eduardo Ruiz-Durántez for his valuable help with the chitosan immobilization experiments.
Icesi University grant number COL0093872-639 funded this study.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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