Effect of metal nanoparticles encapsulated in porous silica on the biphenyl biodegradation by Rhodococcus erythropolis T902.1

Biphenyl is stable and highly hydrophobic, thus having a low availability for degrading microorganisms, which need an aqueous environment for their growth. As a consequence, bioremediation processes are very limited. However, a few studies showed that using a low metal concentration accelerates the biodegradation of pollutants (Yeom and Yoo1997). Nanoparticles are considered as a new generation of compounds to improve environmental remediation and biological processes (Beckers et al. 2013; Zhang 2003). This paper investigated the enhancement effect of nanometre-sized metallic Cu, Ag, Pd or Co, on the biphenyl biodegradation by Rhodococcus erythropolis T902.1. Have been synthesized by a sol–gel process (Lambert et al. 2004). These nanoparticles (NP) of about 2–3 nm were encapsulated in porous silica (SiO2) and were added at low concentration (10-4M) in the M284 minimal medium with 500 ppm biphenyl as source of carbon and energy. The cultures containing Pd or Co produced 30% more biphenyl degraded with a higher Rhodococcus growth than those without NP (positive control) or with silica particles only. On the contrary, the presence of 10-4 M Cu or Ag nanoparticles showed an inhibitory effect on bacterial growth and biphenyl degradation compared to the positive.