## 3 Results and Discussion
### EE2 Biodegradation in Minimal Salt Medium Enriched with Hydrocarbons and Nutrients (MSM + 2%LB)
Those studies presented various EE2 biodegradation rates, from hours to days, indicating that medium composition might play a central role in EE2 biodegradation by the co-metabolic mechanism. Our results revealed the unexpected phenomenon that encapsulated _P. putida_ cells are able to consume EE2 as the sole carbon source. In addition, it was not expected that the biodegradation rate in a medium that was not enriched with hydrocarbons and nutrients would present a faster biodegradation rate compared to the same medium that contained hydrocarbons and nutrients (73.8.1% vs. 56.1%, at T = 72 h, respectively). Since EE2 biodegradation in MSM medium presents better results, it can be assumed that a stationary encapsulated _P. putida_ culture in the presence of ammonia and Mn+2 might use EE2 as a major carbon source or a sole carbon source for metabolic activity and efficient energy generation. This was also shown in the studies of [PERSON] et al. [18] and [PERSON] et al. [26], which showed that _P. putida_ grown in a Mn+2-enriched medium presented almost complete EE2 biodegradation (over 90%) after a short incubation time (17-48 h). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Culture Type** & **Incubation Time (h)** & \begin{tabular}{c} **Initial Concentration** \\ **(mg/L)** \\ \end{tabular} & **Medium Type** & \begin{tabular}{c} **Degradation** \\ **Efficacy (\%)** \\ \end{tabular} & **Reference** \\ \hline SBP-encapsulated & 1 & & & & 11.7 \\ _R. zopfii_ & 24 & 0.9 & MSM + 2\%LB & 75 & This study \\  & 72 & & & 94.9 & \\ \hline _R. zopfii_ (isolate & 8 & 25 & \begin{tabular}{c} MOG + 0.005\% \\ yeast extract \\ \end{tabular} & 70 & [14] \\  & 80 & & & 80 & \\ \hline _R. zopfii_ & 300 & 5 & \begin{tabular}{c} MMSM + yeast \\ extract (0.6 g/L) \\ \end{tabular} & 38 & [8] \\ _R. rhodocrotus_ & 48 & 5 & \begin{tabular}{c} MMSM + yeast \\ extract (0.6 g/L) \\ \end{tabular} & Over 99\% & [8] \\ _R. erythroroglis_ & 13 & 1.4 & \
\begin{tabular}{c} MMSM + adipic acid \\ or glucose \\ \end{tabular} & 47 & [9] \\ _R. equi_ & 65 & 0.5 &
\begin{tabular}{c} MMSM + adipic acid \\ or glucose \\ \end{tabular} & 39 & [9] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Selected literature results for EE2 biodegradation efficacy by _Rhodococcus_ species metabolic activity in the presence of other carbon sources. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Culture Type** & \begin{tabular}{c} **Incubation Time (h)** \\ \end{tabular} & \begin{tabular}{c} **Initial Concentration** \\ **Concentration (mg/L)** \\ \end{tabular} & **Medium Type** & \begin{tabular}{c} **Degradation** \\ **Efficacy (\%)** \\ \end{tabular} & **Reference** \\ \hline SBP-encapsulated & 1 & & & 24.5 \\ _P. putida_ & 24 & 0.9 & MSM + 2\%LB & 56.1 & This study \\  & 72 & & & 73.2 & \\ \hline Nitrified & & & & \\ consortium + & 2–5 days & 0.1 & \
\begin{tabular}{c} Secondary effluents \\ (COD 200 mg/L) \\ \end{tabular} & 75–85 & [27] \\  & 75–85 & [27] \\  & 300h & 5 & MSM + yeast extract (0.6 g/L) & 43 & [8] \\ \hline _P. putida_ & 48 & 0.148 &
\begin{tabular}{c} Boogerd and De Vrind medium \\ + 50 uM MnCl\({}_{2}\) \\ \end{tabular} & -90 & [18] \\ \hline _P. putida_ MnB1 & 17 & 2 & Not available & 96.7 & [26] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Selected literature results for EE2 biodegradation efficacy by co-metabolic activity.