Abstract
The aims of this work were to study the gold leaching by the isolated bacteria from silicate ore. Three strains were isolated and identified as Macrococcus caseolyticus, Acinetobacter calcoaceticus, and Bacillus sp. MBEA40. However, only M. caseolyticus and A. calcoaceticus were capable of gold bioleaching. In order to examine only the effect of microorganisms involved in the gold bioleaching process, minimal medium and ethanol mineral salt medium without amino acids were used for culturing M. caseolyticus and A. calcoaceticus, respectively. The result showed that the growth supernatant (in the absence of microorganisms) of both strains might be more suitable to leaching gold from ore than leaching by microorganisms (in the presence of microorganisms) directly. This might be due to the fact that there is no interference of gold absorption and metal toxicity in microorganisms in the long-term operation. The result also confirmed that amino acids/peptides/proteins produced by microorganisms might be involved in gold bioleaching, as shown in the high-performance liquid chromatography (HPLC) results. The Fourier transform infrared spectroscopy (FTIR) study also found that amine groups and carboxylic groups played important roles in gold bioleaching by M. caseolyticus and A. calcoaceticus. In addition, the bioleaching process had significantly higher gold leaching than mixed pure amino acids due to the growth supernatant containing mixed amino acids/peptides/proteins and other compounds. Therefore, the growth supernatant of M. caseolyticus and A. calcoaceticus can be applied in gold bioleaching under neutral pH conditions, which is considered to be a safe, not corrosive, and environmentally friendly leaching process. This study is also needed further study in order to increase the percentage of gold bioleaching and decrease times.
Highlights
The gold extraction process from ores is the cyanidation method [1]
The results indicated that the Y1 strain belonged to Macrococcus caseolyticus, W1 was identified as Acinetobacter calcoaceticus, and E1 was Bacillus sp
Afterward, isolated strains were investigated for abilities of gold bioleaching from silicate ore
Summary
The gold extraction process from ores is the cyanidation method [1]. This method is the greatest reagent for the gold extraction process and is widely used in various mining areas worldwide. Cyanide has high chemical toxicity for human health and causes environmental problems such as the leakage of cyanide into groundwater, which has a strong effect on humans [1]. This method is difficult to manage and incurs high operating costs [2]. The cyanidation process is still used in various mining industries Another method of interest with a lesser effect on human health and the environment is bioleaching. This method represents the ability of microorganisms to extract gold from various sources, such as electronic waste and mineral ores. The ability of other strains needs to be investigated under mild conditions such as at neutral pH (pH 7) and moderate temperature (30–35 ◦C)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
