Review on chromobacterium violaceum for gold bioleaching from e-waste

Electronic waste, such as printed circuit boards, are an important secondary resource if processed with environment-friendly technologies for obtaining precious metal, such as gold. The gold bioleaching from electronic waste was recently getting paid attractive attention because its available deposit is limited. This review was focused on Chromobacterium violaceum (C. Violaceum), which was a mesophilic, gram-negative, and facultative anaerobe. C. violaceum has the ability of producing CN-which can dissolve gold from the metallic particles of crushed waste printed circuit boards. This article also provided an overview of cyanide-generation mechanism and the optimal conditions for C. violaceum to achieve maximum amount of cyanide generation. The past achievements and recently scenario of recovery studies carried out on the use of some other microorganisms were compared with C. violaceum. And recently some researchers proposed that combined C. violaceum with chemical methods or other mechanism such as iodide, Pseudomonas aeruginosa and Pseudomonas fluorescens which can reinforce the cyanide generation and improve gold-leaching efficiency. The factors affected the microorganisms on cyanide generation were summarized and the proper conditions were also discussed in this article. And present researches of C. violaceum in gold bioleaching had made good progress which the reported leaching efficiency of gold was over 70%. (C) 2016 The Authors. Published by Elsevier B.V.