Oxidative enzymatic response of white-rot fungi to single-walled carbon nanotubes

Although carbon nanomaterials such as single-walled carbon nanotubes (SWCNT) are becoming increasingly prevalent in manufacturing, there is little knowledge on the environmental fate of these materials. Environmental degradation of SWCNT is hindered by their highly condensed aromatic structure as well as the size and aspect ratio, which prevents intracellular degradation and limits microbial decomposition to extracellular processes such as those catalyzed by oxidative enzymes. This study investigates the peroxidase and laccase enzymatic response of the saprotrophic white-rot fungi Trametes versicolor and Phlebia tremellosa when exposed to SWCNTs of different purity and surface chemistry under different growth conditions. Both unpurified, metal catalyst-rich SWCNT and purified, carboxylated SWCNTs promoted significant changes in the oxidative enzyme activity of the fungi while pristine SWCNT did not. These results suggest that functionalization of purified SWCNT is essential to up regulate enzymes that may be capable of decomposing CNT in the environment.