## 3 Degradation and Fate of PFCs in the Environment
### Microbial Degradation Pathway of PFOA and PFOS  
Despite the experimentally illustrated biodegradation of PFOA and PFOS by microbial species [40; 43; 44; 45], there is no available literature confirming a precise biodegradation mechanism of PFOA and PFOS. In the few studies that have reported on PFC biodegradation, \begin{table}
\begin{tabular}{l l c c c c c} \hline \hline \multirow{2}{*}{**Pollutant**} & \multirow{2}{*}{**Microbial Species**} & **Matrix** & **Concentration** & **System** & **Incubation** & **Period (Day)** & **Reference** \\ \cline{3-6}  & & **Conditions** & **(mg/L)** & **Efficacy (\%)** & **Period (Day)** & **Reference** \\ \hline \multirow{4}{*}{PFOA} & _Acidimicrobium_ sp. & 0.1–100 & \textless{}60 & 100 & [40] \\ \cline{3-6}  & strain A6 & & 47 & 77 & 18 & [43] \\ \cline{1-1} \cline{2-6}  & _Pseudomonas parafilva_ & Aerobic & 500 & 48 & 5 & [44] \\ \cline{1-1} \cline{2-6}  & strain A6 & & 0.1–100 & \textless{}60 & 100 & [40] \\ \cline{1-1} \cline{2-6}  & _Pseudomonas aeruginosa_ & & 1.4–1.8 & 67 & 2 & [45] \\ \cline{1-1} \cline{2-6}  & _Pseudomonas_ & & & & & \\ \cline{1-1} \cline{2-6}  & _Pseudomonas_ & & & & & \\ \cline{1-1} \cline{2-6}  & _Pseudomonas_ & & & & & \\ \cline{1-1} \cline{2-6}  & _plecoglossicida_ 2.4-D & & 1000 & 75 & 6 & [46] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Microbial degradation of PFOA and PFOS. particularly PFOA and PFOS, the mechanism is based on the detection of intermediate metabolites. According to [PERSON] et al. [47], this is attributed to PFOA and PFOS having a low redox potential of about \(-450\) mV. Typical microbial oxidizable growth substrates demonstrate redox potentials greater than \(-450\) mV [39; 47]; therefore, at a low redox potential, the transfer of an electron from a substrate for PFC reduction will not be thermodynamically attractive for microbial species. However, as indicated in the previous sections, studies have demonstrated that selected bacteria can degrade PFOA and PFOS under anaerobic [40] and aerobic [43; 44; 45] environments. Besides the redox potential, [PERSON] [41] reported that, in order for a microbe to degrade a PFC, it needs to transport the fluorinated compound into the cell, harbor a recently evolved enzyme to catalyze the C-F bond cleavage, detect the poisonous fluoride ion generated, and protect itself against the fluoride with a fluoride-proton antiporter. However, the disadvantage in C-F bond reduction is that it can be selected against an evolution on the basis that it provides no benefit to the microbial species but drains cellular energy [39]. Despite the shortcomings of C-F bond reduction, selected bacteria which have been exposed to environments with fluoride concentrations exceeding 1 ppm have developed systems to protect themselves against the toxic fluoride ion. [PERSON] et al. [48] reported that bacteria can resist the toxicity of environmental fluoride by expelling the fluoride ion from its cytoplasm by the aid of a proton-coupled fluoride ion antiporter, _E. casseliflaws_ being the common antiporter. The microbe attributes necessary to biodegrade PFCs suggest that bacteria that are found near PFC-producing subjects or in PFC-contaminated environments can develop antiporters and survive the toxic fluoride ion. It is worth noting that in the available literature reporting on PFOA and PFOS degradation by novel microbial species, all reported bacteria were harvested from PFCs contaminated sites, which explains why the reported bacteria can biodegrade PFOA and PFOS. The degradation of PFOA and PFOS by novel bacteria, as reported in the literature [40; 43; 44; 45], can be attributed to certain enzymes cleaving the C-F bond through either oxidation by inserting oxygen atoms or reduction by adding extra electrons to the bond [47]. The dictation of fluoride ions during microbial degradation of PFCs indicates that microbes can break the C-F bond under control environments, which can be either aerobic or anaerobic. [PERSON] et al.