Enhanced biotransformation of nitrobenzene by the synergies of Shewanella species and mediator-functionalized polyurethane foam

Abstract

The performance and mechanism of anaerobic treatment of nitrobenzene using the combination of Shewanella species and anthraquinone-2-sulfonate-modified polyurethane foam (Shewanella/AQS-PUF) were investigated. The results showed that Shewanella/AQS-PUF significantly accelerated nitrobenzene bio-reduction (95.6%) and aniline formation (94.3%) with nitrobenzene removal rate up to 0.13 mM h(-1). Moreover, there were synergistic effects between Shewanella species and AQS-PUF on promoting nitrobenzene biotransformation with 5-fold increase in first-order rate constant compared to that without AQS-PUF. During this process, AQS-PUF could induce Shewanella species to secrete more flavins (0.335 μM) as redox mediator for nitrobenzene bio-reduction. Meanwhile, it was also found that the bound EPS of Shewanella species could act as biocatalyst for nitrobenzene reduction and the addition of flavins enhanced its catalytic activity. This indicated that the EPS of Shewanella species was not only involved in direct bio-reduction of nitrobenzene, but also interacted with secreted flavins to mediate nitrobenzene bio-reduction.