Importance of laccase enzyme and triiodide for gold leaching from silicate ore by marine bacterium Acinetobacter sp.
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Publication Details
Author list: Anusaraporn S., Dolphen R., Thiravetyan P.
Publisher: Elsevier
Publication year: 2022
Journal acronym: PSEP
Volume number: 161
Start page: 788
End page: 800
Number of pages: 13
ISSN: 0957-5820
Languages: English-Great Britain (EN-GB)
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Abstract
The effect of enzymes and other substances on gold bioleaching was investigated. Acinetobacter sp. had a higher gold leaching performance than two strains of Vibrio sp. because it grew well in nutrient broth (NB) medium containing potassium iodide (KI) and produced high levels of both laccase and triiodide (I3-). Under two-step condition of Acinetobacter sp. in NB medium containing KI 10.9 g·L−1 and 1% (w/v) alkali lignin had the highest efficiency in gold leaching. Plausible mechanisms of gold bioleaching involved in biogenic iodide-iodine lixiviant and laccase reaction mechanisms. Laccase produced by Acinetobacter sp. could directly oxidize insoluble gold to soluble gold and also increase iodide oxidation. Afterward, the gold can be oxidized completely in the biogenic iodide-iodine lixiviant to form gold (I) diiodide [AuI2]- or gold (III) tetraiodide [AuI4]-. Interestingly, it was found that silicate ore could act as an inducer of laccase production. Furthermore, alkali lignin addition could increase gold bioleaching due to it can be used as a substrate for laccase production. Therefore, the two-step condition of Acinetobacter sp. could be applied in gold leaching under mild alkaline pH conditions. The advantage of this technology was safer and more environmentally friendly than cyanidation as a conventional extraction. © 2022 The Institution of Chemical Engineers
Keywords
Acinetobacter sp., Silicate ore, Triiodide
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