Biotransformation of multi-walled carbon nanotubes mediated by nanomaterial resistant soil bacteria

In this study, soil bacteria were isolated from nanomaterials (NMs) contaminated goldsmith site and enriched in the presence of multi-walled carbon nanotubes (MWCNT5) in order to obtain resistant bacteria. The isolated resistant bacteria were biochemically and genetically identified as Trabusiella guamensis. Redox-enzyme activity and cell viability assay showed molecular adaptation and no membrane damage in resistant bacteria under MWCNTs stress. The resistant bacteria were allowed to interact with engineered MWCNTs in order to study the bio-transformation in their structure. Raman spectra of biotransformed MWCNT5 revealed increased intensity ratio of I-D/I-G with subsequent formation of C=O and COOH groups on the outer walls of nanotubes that were also confirmed by Fourier transform infrared (FTIR) results. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis) analysis of bio-transformed MWCNT5 revealed surface oxidation of CNTs. The structural changes in concentric walls were also evident from transmission electron microscopy (TEM) images. Our results demonstrated that the biotransformation of MWCNTs was mediated by resistant bacteria through oxidation process. The presented study showed an effective methodology that utilizes NMs resistant microbes for bio-transformation of MWCNTs in different biological settings which will have impact on "green nanotechnology"