Effect of Iron Nanoparticles Synthesized by a Sol-Gel Process on <i>Rhodococcus erythropolis</i> T902.1 for Biphenyl Degradation

Abstract

Nanoparticles (NP S ) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NP S encapsulated in porous silica (SiO 2 ) on the biphenyl biodegradation by Rhodococcus erythropolis T902.1 (RT902.1). The iron NP S (major iron oxide Fe x O y form) were dispersed in the porosity of a SiO 2 support synthesized by sol-gel process. These Fe/SiO 2 NP S offer a stimulating effect on the biodegradation rate of biphenyl, an organic pollutant that is very stable and water-insoluble. This positive impact of NP S on the microbial biodegradation was found to be dependent on the NP S concentration ranging from 10 -6 M to 10 -4 M. After 18 days of incubation the cultures containing NP S at a concentration of 10 -4 M of iron improved RT902.1 growth and degraded 35% more biphenyl than those without NP S (positive control) or with the sole SiO 2 particles. Though the microorganism could not interact directly with the insoluble iron NP S , the results show that about 10% and 35% of the initial 10 -4 M iron NP S encapsulated in the SiO 2 matrix would be incorporated inside or adsorbed on the cell surface respectively and 35% would be released in the supernatant. These results suggest that RT902.1 would produce siderophore-like molecules to attract iron from the porous silica matrix.