Enhancing gold recovery from electronic waste via lixiviant metabolic engineering in Chromobacterium violaceum

Abstract

Conventional leaching (extraction) methods for gold recovery from electronic waste involve the use of strong acids and pose considerable threat to the environment. The alternative use of bioleaching microbes for gold recovery is non-pollutive and relies on the secretion of a lixiviant or (bio)chemical such as cyanide for extraction of gold from electronic waste. However, widespread industrial use of bioleaching microbes has been constrained by the limited cyanogenic capabilities of lixiviant-producing microorganisms such as Chromobacterium violaceum. Here we show the construction of a metabolically-engineered strain of Chromobacterium violaceum that produces more (70%) cyanide lixiviant and recovers more than twice as much gold from electronic waste compared to wild-type bacteria. Comparative proteome analyses suggested the possibility of further enhancement in cyanogenesis through subsequent metabolic engineering. Our results demonstrated the utility of lixiviant metabolic engineering in the construction of enhanced bioleaching microbes for the bioleaching of precious metals from electronic waste.

Bio-Reclamation of Strategic and Energy Critical Metals from Secondary Resources

“…They suggested an improved bio-reclamation of gold can be achieved by reducing the cyanide consumption from the copper containing material, and hence, proposed to substantially decrease copper content prior to undergo for biogenic cyanidation of precious metals. Recently, Tay et al [59] could produce 70% more cyanide by metabolically-engineered strains of Chromobacterium violaceum, pTAC and pBAD in as compared to the cyanide generated by wild culture of Chromobacterium violaceum. Such a high amount of cyanide yielded more than twice the amount of gold leaching as well.…”

Improving Gold (Bio)Leaching Efficiency Through Pretreatment Using Hydrogen Peroxide Assisted Sulfuric Acid

“…Both bioleaching and spent medium leaching were carried out over a period of 8 days. Samples were collected daily and centrifuged (11 000 g for 15 min); the supernatant was filtered (0.45 μm) before metal analysis using ICP‐MS .…”

An Overview of Reclaimed Wastewater Reuse in Gold Heap Leaching

“…Hence, these microorganisms can play an active role in gold extraction (Campbell et al 2001;Tay et al 2013). Among the aforementioned species, C. violaceum is noteworthy because of its remarkable cyanide production capacity, which can significantly affect gold extraction.…”