Interactions between bacteria and heteroatom-modified nanoporous carbon: The influence of nitrogen and sulfur doping

Heteroatom-doped carbon structures have successfully entered the field of advanced functional materials but their impact on living organisms is still poorly examined. Interactions between typical Gram-negative bacteria Escherichia coli, Gram-positive Bacillus cereus and heteroatom-doped nanoporous carbons are studied in this paper. Four types of carbonaceous materials, that is N-doped, S-doped, S/N-co-doped and undoped carbon gels, are considered. Respirometric measurements, dehydrogenases activity and viability tests were conducted to assess the toxicity of the doped carbons against bacteria. The heteroatom-doped and dopant-free carbon gels do not cause an inhibition of bacterial growth nor a lethal effect. On the contrary, we demonstrate that the doped carbons enhance microbial activity. The adhesion of bacteria to the carbon surface was investigated based on the adsorption studies and biofilm formation. It is demonstrated that the doping of carbons with nitrogen induces surface acidity and hydrophilicity, which in turn significantly enhances the bacteria sorption. Unlike the S-doped or undoped materials, the N-doped carbons are characterized by high bacterial affinity, even when compared to efficient bacteria adsorbents, e.g. active carbon Norit. The results obtained demonstrate that N-containing carbon gels support bacterial proliferation and as such may constitute attractive materials for wastewater treatment technologies as well as bioelectrochemical processes.