Purpose: To demonstrate eco-friendly biosynthesis of gold nanoparticles by Enterobacteriaceae.

Methods: Pure colonies of nine different bacteria from the Enterobacteriaceae family were separated from water and cultured in Luria Bertani broth medium. Their respective supernatants were examined for ability to produce gold nanoparticles. In this step, 1 mM solution of Gold(III) chloride trihydrate H(AuCl4) added to reaction matrices (supernatant) separately. The reaction was performed in a dark environment at 37 ºC. After 24 h, it was observed that the color of the solutions turned to dark purple from light yellow. The gold nanoparticles were characterized by UV-Visible spectroscopy, dynamic light scattering, scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR) for yield, particle size, shape and presence of different functional groups, respectively. The nanoparticles were centrifuged and re-dispersed in double distilled water thrice to purify them for FTIR studies.

Results: The gold nanoparticles were fairly uniform in size, spherical in shape and with Z-average diameter ranging from 11.8 to 459 nm depending on the bacteria used. FTIR spectra revealed the presence of various functional groups in the gold nanoparticles which were also present in the bacterial extract.

Conclusion: The current approach suggests that rapid synthesis of nanoparticles would be feasible in developing a biological process for mass scale production of gold nanoparticles.