5. Discussion

4.2. Results from high performance liquid chromatography (HPLC)

146 Wastewater and Water Quality

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

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

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

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 of exposure to the bacteria in wastewater.
