Joint effects of carbon nanotubes and copper oxide nanoparticles on fermentation metabolism towards Saccharofermentans acetigenes: Enhancing environmental adaptability and transcriptional expression

Abstract In this study, the joint effects of widely used copper oxide nanoparticles (CuO NPs) and multi-walled carbon nanotubes (MWCNTs) on the fermentation metabolism of a model acetogenic bacterium Saccharofermentans acetigenes were investigated and the underlying mechanisms were further explored. The presence of sole CuO NPs or MWCNTs severely inhibited the acetate generation, while their co-existences did not further decrease the acetate yield as expected. Further analysis indicated the joint effects facilitated the enhancement of bacterial stimulus response to the environment and interspecies communication, which improved adaptive capacity to the adverse environment involved in nanomaterials. Meanwhile, the co-existence reduced inhibitory effects of sole nanomaterial on the gene expressions and catalytic activities of key enzymes involved in glycolysis and pyruvate metabolism. Therefore, the joint effects could enhance environmental adaptation of S. acetigenes and transcriptional expressions of key enzymes for acetic acid production-related processes, alleviating the inhibition of CuO NPs to acetate production.