Biosynthesis of gold nanoparticles using cell-free extracts of Magnusiomyces ingens LH-F1 for nitrophenols reduction.

A green and eco-friendly method for the synthesis of gold nanoparticles (AuNPs) was developed using the cell-free extracts of a yeast strain Magnusiomyces ingens LH-F1. UV-vis spectra showed a distinct absorption band at ~ 540 nm, corresponding to the surface plasmon resonance of AuNPs. Transmission electron microscopy images revealed that the shapes of AuNPs were almost spherical and pseudo-spherical. Fourier transform infrared spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses suggested that some proteins containing amino- and carboxyl-groups in the cell-free extracts were absorbed on the surface of nanoparticles, which could act as reducing and capping agents for AuNPs synthesis. Furthermore, with the concentration of cell-free extracts increasing from 25 to 200 mg L-1, the average size of AuNPs decreased from 28.3 to 20.3 nm. Meanwhile, the morphology became more uniform with less irregular shapes. In addition, the as-synthesized AuNPs showed an excellent catalytic activity for nitrophenols reduction (i.e., 4-nitrophenol, 3-nitrophenol and 2-nitrophenol) in the presence of excess NaBH4. The catalytic rate constant of nitrophenols reduction was also dependent on cell-free extract concentration. The larger AuNPs synthesized by less cell-free extracts were covered with a thinner corona and showed better capacity for reducing nitrophenols. This study suggested that the as-synthesized AuNPs could be employed as efficient catalysts in reduction of organic contaminants.