4.1. Degradation of PCBs by Pseudomonas aeruginosa

Samples of wastewater from the Notwane Sewage Treatment Plant were used in this study to find out the degree of biodegradation of PCBs in wastewater un-inoculated and inoculated with the test organism. Spectral changes (a shift in wavelength (λmax) in nm), detected using the UVvisible spectrophotometer, were used as an indication that the compounds were broken down into new products. The results of the wavemax (λmax) nm obtained are presented in Figure 2.

The results shown by chromatogram indicated that there was a shift in λmax from 224 to 270 nm in 0 h of incubation to 96 h of incubation at 30C on a rotary shaker in the dark. These results were obtained using a Cary 300 UV-visible spectrophotometer at a wavelength range of 200–800 nm. The results were an indication that isolates Pseudomonas aeruginosa was able to degrade Aroclor 1260 into chlorobenzoates and derivatives, which have wavelength ranging from 244 to 270 nm, hence the shift in wavelength.

Figure 2. Spectral changes of PCB degradation in water inoculated with isolate Pseudomonas aeruginosa.

PCB standard presented in Figure 3 showed that there were several compounds in the Aroclor; thus, the many picks, which are not found when the same treatment was extended to the

The Role of Bacteria on the Breakdown of Recalcitrant Polychlorinated Biphenyls (PCBs) Compounds in Wastewater

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The chromatogram shows that the components of the standard had retention times ranging from 3.647 to 13.119 min. The components picked by the instrument are indicated by the red line marking the beginning and ending of the peak. The instrument could not detect the actual

The wastewater was sterilized and thereafter inoculated with the test organism and PCBs mixture added. Figure 4 shows that no peaks were picked by the HPLC. This is an indication that the polychlorinated biphenyls added to the wastewater were completely broken down by

Representation of Figure 4 is a clear indication that there were no detectable amounts of compounds after Aroclor was subjected to bacterial treatment. The compounds were broken down in 5 days. There are no peaks shown as compared to the chromatogram shown in Figure 3.

The wavelength maximum (λmax) observed after 96 h ranged from 264 to 269 nm on average for PCBs (Figure 2). These results indicated that the PCBs were broken down forming new products with different wavelength and thus the change. This implies that the bacteria were able to use them as their sole source of carbon; thus, the biodegradation of the PCBs added to wastewater. The shifts are an indication of the presence of initial ring oxidation metabolites and ring fission metabolites [19, 47]. PCBs first get degraded into chlorobenzoates [47] that have been found to have λmax ranging from 210 to 214 nm in the B-band and 244 to 270 nm in the C-band when dissolved in water [48], a range that was observed in the results obtained after 24 h of culturing the organism used in this study in PCBs Aroclor mixture, results of which are shown in Figure 2. The results depicted that the bacteria was able to breakdown the PCBs, which were similar to results in a similar studies by Vrchotova et al. and Seeger et al. [47, 49]. In their studies [47, 49], the product chlorobenzoate was biodegraded into benzoate and eventually pyruvate and

The HPLC run confirmed that the compound was biodegraded by the bacteria isolate Pseudomonas aeruginosa as presented in Figures 3 and 4, which was also proved by Heider and Rabus, Roy et al. and Raja et al. [38, 46, 50] in their studies. No PCB compound was detected after 96 h

Pseudomonas aeruginosa, isolated from wastewater in the Notwane Sewage Treatment Plant was successfully used in biodegradation of recalcitrant polychlorinated biphenyls (PCBs). This having been successfully employed at the micro level, and further tests can be carried out to

isolate Pseudomonas aeruginosa resulting in complete elimination.

acetyladehyde, which are essential in the tricarboxylic cycle (TCA) [47, 49].

of exposure to the bacteria in wastewater.

experiment, resulted in Figure 4.

names of the compounds though.

5. Discussion

6. Conclusion

Figure 3. HPLC chromatogram for PCBs standard using a florescence detector method at 10 μl injection volume.

#### 4.2. Results from high performance liquid chromatography (HPLC)

HPLC chromatogram depicted differences in picks obtained for the experiments, the controls, and the standards. Although concentrations were not determined, no PCBs were detected by HPLC after 96 h of incubation. This was an indication that the bacteria degraded the compounds, hence the chromatogram shown in Figure 4. The chromatogram obtained for the experiments was compared with the chromatogram for the PCB standard using the retention times for the compounds in the standard, which was represented in Figure 3. The results for

Figure 4. Chromatogram for PCB biodegradation experiment after 96 h of incubation.

PCB standard presented in Figure 3 showed that there were several compounds in the Aroclor; thus, the many picks, which are not found when the same treatment was extended to the experiment, resulted in Figure 4.

The chromatogram shows that the components of the standard had retention times ranging from 3.647 to 13.119 min. The components picked by the instrument are indicated by the red line marking the beginning and ending of the peak. The instrument could not detect the actual names of the compounds though.

The wastewater was sterilized and thereafter inoculated with the test organism and PCBs mixture added. Figure 4 shows that no peaks were picked by the HPLC. This is an indication that the polychlorinated biphenyls added to the wastewater were completely broken down by isolate Pseudomonas aeruginosa resulting in complete elimination.

Representation of Figure 4 is a clear indication that there were no detectable amounts of compounds after Aroclor was subjected to bacterial treatment. The compounds were broken down in 5 days. There are no peaks shown as compared to the chromatogram shown in Figure 3.
