English abstract
Oil spills could occur during oil production and transportation and many petroleum compounds contaminate the environment. These compounds are toxic to the environment and have to be cleaned. Bioremediation is the most environmentally friendly and cost effective method that can successfully remove contamination by converting oil completely to CO2. Bioremediation approaches such as bioaugmentation involving the addition of bacteria and biostimulation involving the addition of organic and inorganic nutrients have been widely used to clean up oil contamination. The research in this thesis aims at identifying 46 isolated oil degrading bacterial strains and testing their ability to degrade alkanes and to produce compounds that enhance biodegradation such as biosurfactants, biopolymers and fatty acids. A bacterial consortium out of these strains was designed and used to bioremediate two different oil-polluted sediments in the presence and absence of inorganic nutrients. Oil degradation was assessed by measuring the formation of CO2 and by comparing the concentrations of hydrocarbon compounds before and after the treatments using Gas Chromatography-Mass Spectrometry (GC-MS).
The 16S rRNA sequences of the cultured strains showed that they belonged to known oil-degrading bacterial genera such as Pseudomonas, Alcanivorax, Marinobacter and Halomonas. Biopolymer and biosurfactant production was assessed using Quarzviskosimeter and tensiometer, respectively and showed that none of the strains produced these compounds using acetate and sucrose as carbon sources. The strains had at least 6 fatty acids with hexadecanoate and its derivatives as the most dominant ones. Representative strains could grow much better on C13-C19 alkanes than C5-C7 alkanes. The best bioremediation efficiency was achieved by a combination of both bioaugmentation and biostimulation, where CO2 elevation was 6.73% and 9.58% for PDO and KH sediments, respectively. Hydrocarbon analysis showed a decrease in the treated samples, which means that degradation took place. We conclude that indigenous oil-degrading bacteria from Omani soils can be useful in the bioremediation of oil-polluted sediments in the region.
