Investigation on indigenous bacteria for individual BTEX degradation potentials and relative pathways used

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: Alper Yavaş

Asıl Danışman (Eş Danışmanlı Tezler İçin): BÜLENT İÇGEN

Eş Danışman: MAHMUT PARLAKTUNA

Özet:

Monoaromatic hydrocarbons including benzene, toluene, ethylbenzene and xylene collectively called as BTEX are found in the composition of crude oil and gasoline as an additive and thought to be the most serious contaminants of soil and groundwater. It is expected that indigenous bacteria isolated from petroleum hydrocarbon contaminated sites probably have degradation potential for the BTEX compounds. In this study, out of 22, 19 bacterial strains were selected as potential degraders for at least one of the BTEX compounds. The degradation abilities of the bacterial strains were determined by using HS-GC/MS and 9 bacterial strains namely R. plancticola Ag11, S. aureus Ba01, S. nematodiphila Ba11, A. calcoaceticus Fe10, P. koreensis Hg10, P. koreensis Hg11, S. nematodiphila Mn11, A. johnsonii Sb01 and M. luteus Sr11 were chosen as efficient degraders for pathway analyses. Polymerase Chain Reaction (PCR) was first performed for the detection of catabolic genes. PCR results revealed that most of the bacterial strains harbored the todC1 gene and only two of them carried the tbmD gene. To evaluate biodegradation pathways, BTEX intermediates produced during degradation were also analyzed by using GC/MS. The results showed that monooxygenation pathway was more common within bacterial strains although dioxygenation genotype (todC1) was more prevalent. Intermediate analyses and PCR-detection of catabolic genes revealed that benzene was degraded by R. plancticola Ag11 and M. luteus Sr11 through monooxygenation pathway. Toluene was metabolized through side chain monooxygenation pathway by the strain A. calcoaceticus Fe10 and ring monooxygenation pathway by the strain M. luteus Sr11. During ethylbenzene degradation by R. plancticola Ag11, P. koreensis Hg11 and S. nematodiphila Mn11 styrene pathway was mainly used. Comparison of PCR-detection and intermediate analysis results led to conclude that new primer sets were required to detect all possible subfamilies of the ring hydroxylating monooxygenase and side chain monooxygenase genes. The study revealed five efficient bacterial strains namely R. planticola Ag11, A. calcoaceticus Fe10, P. koreensis Hg11, S. nematodiphila Mn11 and M. luteus Sr11 with their corresponding pathways for aerobic degradation of the individual BTEX compounds.