Possible mechanism of gallium bioleaching from gallium nitride (GAN) by Arthrobacter creatinolyticus: Role of amino acids/peptides/proteins bindings with gallium

The objectives of this work were to screen and characterize heterotrophic bacteria for gallium nitride (GaN) leaching; and to study the involved mechanism of bacterial leaching of Ga from GaN. Ga in the form of GaN has been extensively used as a semiconductor substrate material. The advantage of bioleaching for gallium recovery is the fact that it is a safer, environmentally-friendly method and includes energy-saving processes, which can leach metals at relatively low concentrations. Three bacterial isolates were isolated from cadmium-, and arsenic-contaminated soil in the presence of GaN. NKS4 showed the highest efficiency in Ga leaching at approximately 18% after 15 days, and the system pH was 9. The analysis of 16S rDNA sequences indicated that strain NKS4 was characterized and identified as Arthrobacter creatinolyticus (A. creatinolyticus). Further investigation revealed that the ability of Ga leaching from GaN by this bacterium involved amino acids. Fourier transform infrared spectroscopy (FTIR) was used to investigate the interaction of Ga and amino acids/peptides/proteins which were secreted from this bacteria.