# Bioremediation of Crude Oil by _Corynebacterium stationis_ CsPe-1: A Preliminary In Vitro Study
## 3 Results and Discussion  
Table 1 shows the BOD\({}_{5}\) values that increased after 20 days of oil treatment with _C. stationis_ CsPe-1. This result is very different from the value obtained with another C. _stationis_ CsPe-1 strain, which was able to reduce BOD\({}_{5}\) by 98.4% and COD by 97.5% in oil-contaminated soils after 40 days [48]. This could be explained by the fact that after 20 days, C. _stationis_ CsPe-1 is already in its stationary phase of growth, and oxygen consumption by the surviving population has been reported to increase during this phase [49]. In Table 2, it was observed that at both 10% and 15% inoculum concentrations, the initial and final values of oils and fats showed significant differences (_p_ < 0.05). However, no significant differences were found when comparing these values between the two concentrations (_p_ > 0.05). In this case, an aerobic degradation process was carried out, in which the biodegradation of PAHs is initiated by the enzyme oxygenase, which, in the presence of oxygen, catalyzes the addition of oxygen atoms to aromatic compounds. The result is the formation of catechol or protocatechol with hydroxyl groups. Then, alcohol dehydrogenase enzymes convert alcohol to aldehyde and then to fatty acids. These enter the \(\beta\)-oxidation process and acetyl CoA is produced, which reacts with fatty acids in the cytosol of prokaryotic cells or can also enter the citric acid (TCA) cycle [16; 50; 51; 52]. Similar results have been reported with other bacterial strains of the genera _Pseudomonas_ and _Rhodococcus_[53; 54; 55]. However, _Corynebacterium_ stand out for their ability to adapt to a wide range of environmental conditions, which makes them particularly useful for bioremediation in various contaminated environments [56; 57]. The effectiveness of _C. stationis_ CsPe-1 can be attributed to its ability to produce biosurfactants, which enhance the solubility of hydrocarbon molecules in the aqueous medium, facilitating their access to bacterial cells [58]. These biosurfactants allow for the emulsification of oils, favoring the \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{3}{c}{**Inoculum Concentration**} \\ \cline{2-5}  & **Control** & **10\%** & **15\%** & **t (\(p\)-Value)** \\ \hline Oils and Fats (Initial) & 4154.00 & 4675.90 & 4297.72 & 1.734 (0.158) \\ \hline Oils and Fats (Final) & 4153.85 & 1813.27 & 1648.62 & 1.459 (0.218) \\ \hline t (\(p\)-value) & & 14 (0.005) & 23.54 (0.002) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Analysis of BOD\({}_{5}\) and COD in oil degradation systems inoculated with C. _stationis_ CsPe-1 contained in a stirred bioreactor. decomposition of hydrocarbons into more manageable units for the action of microbial enzymes. Notably, in this study, the 15% inoculum concentration exhibited a more substantial reduction in oils and fats compared to the 10% treatment, which can be attributed to the enhanced biosurfactant production, thereby increasing the bioavailability of hydrocarbons for degradation. In Figure 1a, a significant reduction in the concentration of the TPH and petroleum fractions due to the action of _C. stationi_s CsPe-1 is evident at both the 10 and 15% inoculum concentrations. The observed variations in the reduced concentration may be attributable to the structural characteristics inherent to each fraction. At a particular inoculum concentration, a lower concentration is observed, with the exception of fraction 2. As shown in Figure 1b, the highest percentage reductions were achieved in all fractions when the 15% inoculum of _C. stationi_s CsPe-1 was used. Fraction 3 exhibited a notably higher percentage of reduction, reaching a value of 79.94% (127.4 mg L\({}^{-1}\)) with the 15% inoculum. The degradation of petroleum hydrocarbons has been linked to the presence of certain enzymes, such as oxygenase and peroxidase, as well as the production of biosurfactants, as evidenced in the case of _Corynebacterium aurimucosum_[37; 59].