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Effect of metal ions and metal nanoparticles encapsulated in porous silica on biodegradation kinetics for biphenyl

par Wannoussa, W.;Hiligsmann, Serge ;Masy, T.;Lambert, S.;Heinrichs, B.;Al-Ahmad, A.;Weekers, Frédéric;Thonart, P.
Référence Journal of sol-gel science and technology, 75, page (235-245)
Publication Publié, 2015

Article révisé par les pairs

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Résumé :

[en] Biodegradation of biphenyl was carried out by Rhodococcus erythropolis T902.1 in presence ofnanometer-sized metallic (Co, Pd, Ag and Cu) nanoparticles (NPS) synthesized by the sol-gel process. In order toprevent their agglomeration, the metallic NPs (1-2 nm diameter) were anchored inside microporous silica crystallitesand named Co/SiO2, Pd/SiO2, Ag/SiO2 and Cu/SiO2 samples respectively. They were added at low concentrations of10-6 M, 10-5 M and 10-4 M of metal in the culture medium and their impact was compared with that of the simplemetal ions added as cobalt, palladium, silver or copper salts. The cultures containing Pd/SiO2 or Co/SiO2 samples at10-4 M of metal achieved a 50% higher biphenyl degradation yield after 18 days of incubation and improvedRhodococcus erythropolis T902.1 growth compared with those without (positive control) or with silica particlesonly. The highest biodegradation performance, i.e. 107pm 3 ppm/day, which was about 85% higher than in controlconditions without NPs, was recorded in 250 ml baffled flasks stirred at 150 rpm with Co/SiO2 sample at 10-4 M Co.Furthermore, the stimulating effect of NPs on biphenyl biodegradation seems to also depend on the thermaltreatment conditions applied to NPs since the experimental results indicated that, after calcination, the cobalt oxideNPs at a concentration of 10-4 M were more effective than the reduced cobalt NPs with a degradation yield of81pm 1% and 77pm 2% respectively after 18 days. On the other hand, the results showed that the addition of 10-4 M ofCu2+ or Ag+ ions or the addition of Cu/SiO2 or Ag/SiO2 samples at 10-4 M of metal have an inhibitory effect onbiphenyl biodegradation. However, Cu+2 and Ag+ ions were more toxic to the Rhodococcus erythropolis T902.1bacteria than the respective Cu or Ag NPS anchored inside silica particles. Moreover, this work showed that in theseconditions, the activity of catechol 1, 2-dioxygenase (a critical enzyme in aromatic biodegradation pathway) wasseverely inhibited, whereas the presence of 10-4 M of Co2+ ions or Co/SiO2 sample stimulated the enzyme activitycompared to the conditions without NPs.