Research On Degradation Performance, Mechanism And Application Of Petroleum Hydrocarbon Degrading Bacteria

In this study, the high-efficient petroleum hydrocarbon degrading bacteriaBrevibacillus panacihumi W25and Gordonia alkanivorans W33were thoroughlystudied, such as the performance and mechanism of oil degradation of W25and W33together with their application in the drill cuttings disposal. The main conclusionswere shown as follows:The results of1%crude oil degradated by W25, W33and their mixture showedthat the degradation percentages were83.10%,91.73%and96.42%after nine daysdegradation, respectively. It was concluded that W25and W33both had a widedegradation spectrum and the ability to degradate long-chain alkane, which showedthat they both had great application potential. In the phenanthrene (as the only carbonsource) degradating experiments by W25and W33, W25seemed not to have theability to degrade phenanthrene; while W33had a16.85%degradation percentage in12days. For the mixture, it was20.13%, which showed that there were synergisticdegradation effects between W25and W33. Comparing with the crude oil withoutphenanthrene, phenanthrene did not have much effect on the crude oil degradation,while the degradation rate of phenanthrene was greatly improved, reaching to87.65%.In one word, the degradation effects of mixture of W25and W33were much betterthan single bacterium, which demonstrated the synergy of the two bacteria. Thisindicated that the mixed bacteria had great application potential.The whole genome sequences of W33was analyzed, and the comprehensiveanalysis of W25and W33oil degradation genes was also proceeded to study thedegradation mechanism. After the annotated genes analysis of W25,7genes werecomfirmed to be involved in hydrocarbon degradation. The analysis result of W33showed that9genes were comfirmed to be involved in hydrocarbon degradation andall of them were tested by Q-PCR. Considering the degradation properties of W25andW33, the study of degradation mechanisms of straight-chain alkanes, branchedalkanes and PAHs of W25and W33was implemented under gene level.To improve the practical application of W25and W33, fermentation conditionswere optimized to achieve maximum biomass, including the optimization of shakeflask,5L fermenter and20L fermenter expanding culture. The most suitable fermentation conditions for two strains were found, and the fermentation efficiencywas increased.The effects of the system of W25and W33mixture in practical applications wereverified.The laboratory orthogonal experiments were conducted on drill cuttings, andthe effect of bacteria, fertilizers and surfactants on the compost was tested. The resultsshowed that the bacteria had the biggest influence and fertilizers were the second.According to the results, pilot scale drilling cuttings biological compost treatmentexperiments were conducted by adding W25and W33. After73days of test, thedegradation percentages reached to69.04%, while the control group was merely17.75%. This indicated that the two strains had large potential for industrialapplications.