Exploratory Response Essay

The exploratory phase (Exp No. 1) has highlighted bio-reduction ferrihydrite by Shewanella oneidensis MR-1, which occurs only in the presence of formate (carbon source and electron). The Exp # 2 showed that the presence of the bacterium and iron oxide in the reaction medium (E-Sh-Ox) promotes the disappearance of endosulfan but inhibits its hydrolysis (and thus its transformation into ES-diol ) susceptiblement by more effective adsorption phenomenon. It is observed in this case 89.45% α + β O disappeared for 33.92% of ES-diol product, 56% of ES α + β missing. However, by amending formate (carbon source and electron) to medium (one obtains E-Sh-Ox-f), the production rate in ES-diol after 14 days of incubation reaches 81.93 % to 93.31% α + β
O disappeared. This could mean that ferrihydrite recognized for its adsorption capacity would be to the detriment of hydrolysis (main degradation processes of α + β ES in aqueous medium and anaerobic conditions) ES α + β in ES-diol . This leaves suggest that bio-reduction of ferrihydrite favors hydrolysis ES α + β by the adsorption of its diminution. Also, the ES-diol content produced by E-Sh-f (55.76%) and Ef (48.60%) and 84.99% against 83.73 α + β O disappeared are not significantly different to the last day of incubation. It can be inferred that the bacterium has a positive effect on the degradation of the α + β ES but not on its disappearance even in the absence of iron oxide. Finally, it appears a disappearance rate in ES + β α E-Sh-Ox-f> E-Sh-Ox> E-Sh-f ~ Ef while the production rate in ES-diol system E- Sh-Ox-f >> E-sh-e ~ Ef >> E-sh-Ox, thus involving E-Ox-sh-sh-f >>> E-Ox.
To meet the objective of this work, one can conclude that the bacteria in the presence of ferrihydrite available with a carbon source and electron positively impact on the degradation of α + β ES.
The degradation process in this case out put by hydrolysis could be biological or abiotic under the influence of Fe (II) product. Fe (II) produced in the E-Sh-Ox-f system could induce degradation of α + β ES, or in another case is adsorbed on ferrihydrite and the complex formed may degrade the α ES + β. This hypothesis can be verified by an experiment for E-Fe modalities (II) -f, E-Fe (II) -Ox-f and Ef in order to observe the degradation rates depending on the presence Fe (II) and Fe (II) complex -Ox. The missing part O α + β could be transformed into another compound or then the ES-product diol to be converted in turn into ES-ether, ES-hydroxy-ether or other product. This could be verified by a UHPLC analysis coupled with mass spectroscopy (UHPLC-MS). It would be interesting to determine the SE of the adsorption kinetics of α + β and ES-diol by performing sorption isotherms on ferrihydrite and the reactor walls. We could do an analysis on the particles in the medium after bio-reduction to see if there would be a new mineral formed. In the case where there is forming a new mineral, one would carry out an analysis. Once identified mineral, it could also perform experiments in establishing E-f-new mineral terms, E-Fe (II) -New mineral-f, E-Fe (II) -New mineral-Ox-f and Ef to evaluate
its presence on the degradability of α + β ES.