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Minerals 2018, 8(3), 81; https://doi.org/10.3390/min8030081

Size-Controlled Production of Gold Bionanoparticles Using the Extremely Acidophilic Fe(III)-Reducing Bacterium, Acidocella aromatica

Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
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Received: 24 January 2018 / Revised: 14 February 2018 / Accepted: 22 February 2018 / Published: 26 February 2018
(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)
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Abstract

Recycling of gold-bearing “urban mine” resources, such as waste printed circuit boards (PCBs), is attracting an increasing interest. Some of the gold leaching techniques utilize acidic lixiviants and in order to eventually target such acidic leachates, the utility of the acidophilic Fe(III)-reducing heterotrophic bacterium, Acidocella (Ac.) aromatica PFBC was evaluated for production of Au(0) bionanoparticles (bio-AuNPs). Au(III) ions (as AuCl4, initially 10 mg/L), were readily adsorbed onto the slightly-positively charged Ac. aromatica cell surface and transported into cytoplasm to successfully form intracellular bio-AuNPs in a simple one-step microbiological reaction. Generally, increasing the initial concentration of formate as e-donor corresponded to faster Au(III) bioreduction and a greater number of Au(0) nucleation sites with less crystal growth within 40–60 h: i.e., use of 1, 5, 10, or 20 mM formate led to production of bio-AuNPs of 48, 24, 13, or 12 nm in mean particle size with 2.3, 17, 62, and 97 particles/cell, respectively. Addition of Cu2+ as an enzymatic inhibitor significantly decreased the number of Au(0) nucleation sites but enhanced crystal growth of individual particles. As a result, the manipulation of the e-donor concentration combined with an enzyme inhibitor enabled the 3-grade size-control of bio-AuNPs (nearly within a normal distribution) at 48, 26 or 13 nm by use of 1 mM formate, 20 mM formate (+Cu2+) or 10 mM formate, respectively, from highly acidic, dilute Au(III) solutions. View Full-Text
Keywords: gold nanoparticles; Acidocella aromatica PFBC; Fe(III)-reducing bacterium; acidophilic microorganism; size-control gold nanoparticles; Acidocella aromatica PFBC; Fe(III)-reducing bacterium; acidophilic microorganism; size-control
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Rizki, I.N.; Okibe, N. Size-Controlled Production of Gold Bionanoparticles Using the Extremely Acidophilic Fe(III)-Reducing Bacterium, Acidocella aromatica. Minerals 2018, 8, 81.

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