Enhanced bioreduction of nitrobenzene by reduced graphene oxide materials: effects of surface modification and coexisting soluble electron shuttles

Reduced graphene oxide (rGO) can enhance the bioreduction of nitrobenzene by Shewanella oneidensis MR1. The effects of surface modification and coexisting soluble electron shuttles on rGO-enhanced bioreduction of nitrobenzene were investigated here. The results showed that rGO enhanced the secretion of extracellular polymeric substance and the bioreduction of nitrobenzene of several folds. No inhibition effect on nitrobenzene bioreduction was observed even when the concentration of rGO was as high as 200 mg/L. The surface modification of rGO might affect the electrical conductivity which was assumed as one of the main factors that contributed to the enhancement of nitrobenzene bioreduction by rGO materials. Moreover, the coexisting electron shuttles further enhanced the rGO-mediated nitrobenzene bioreduction. After the simultaneous addition of flavin mononucleotide (10 mu M) and rGO (50 mg/L), the reduction rate increased 7.8 times to 424.98 +/- 7.84 mg (nitrobenzene)/(g (dry cell).h), which was higher than those ever reported.