Biodegradation of Petroleum Hydrocarbons by Indigenous Bacteria and Microbial Consortium under Different pH and Temperature Conditions: An HPLC Based Study

Petroleum hydrocarbon biodegradation is a viable environmental
conservation tool that can be used in the remediation of the oily atmosphere.
In the given study, isolated native bacteria and a microbial community were
tested based on their capacity to break down petroleum hydrocarbons in
different pH and temperature conditions. Bacterial isolates were acquired in
oil-contaminated soil and it was filtered in terms of its capability to utilize
hydrocarbons. The effectiveness of biodegradation was evaluated in biomass
production, optical index density, emulsification index and high
performance liquid chromatography (HPLC) of the various aromatic
compounds of interest. Two hundred and forty eight bacteria isolates were
obtained on the oil-infested soils of which nine of them showed high ability
of degrading PAH. HPLC analysis confirmed a high level of removal of the
high-molecular-weight PAHs such as BaA, Chrysene, BbF, BaP, and BKF.
Rhodococcus sp. provided the most efficient degradation efficiency of 88 per
cent overall PAH removal with Pseudomonas putida (87 per cent) and
Pseudomonas luteola (80 per cent) as the second and third best respectively.
Micrococcus luteus recorded the least degradation (39%). One-way ANOVA
statistical analysis showed that isolate differences were statistically
significant (p < 0.05). The pH had a significant impact on PAH degradation
(p < 0.05). Optimum degradation was seen at pH 7-8 where the microbial
consortium performed better than the individual isolates. The consortium
reported the greatest level of biodegradation in a neutral condition, which
matched the highest biomass (0.294 g/L) and emulsification index
(98%).Temperature also played a great role in degradation of PAH (p < 0.05).
The consortium was best removed at temperatures of 30 o C, where the
consortium had the best biomass (0.294 g/L) and high emulsification capacity
(88 percent). Most isolates were found to be affected by thermal stress at 35C,
allowing Bacillus cereus to outperform the microbial consortium, with the
consortium being more metabolically cooperative and complementary in
terms of enzymatic activity to effectively degrade PAH under favorable pH
(7- 8) and moderate temperature (30°C). These results indicate good
experimental support to the application of indigenous microbial consortia in
the effective removal of petroleum hydrocarbons bioremediation.