Microorganisms Utilizing Sulfur-Containing Hydrocarbons
Bacteria which are able to transform sulfur-containing compounds, for utilization of either the sulfur or the carbon skeleton, are widely spread in nature. In this chapter, we focus on those bacteria able to degrade heterocyclic hydrocarbons by extracting
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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2130
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Microbiological Degradation and Transformation of S-Heterocycles . . . . . . . . . . . . 2130
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Sulfur-Specific Desulfurization of DBT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2131 Microorganisms and Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2131 Genes and Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2132 Utilization of Alkyl-Derivatives of DBT and Desulfurization of Real Oil Fractions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2136
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Sulfur-Specific Desulfurization of other Organosulfur Compounds . . . . . . . . . . . . . 2136
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Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2137
K. N. Timmis (ed.), Handbook of Hydrocarbon and Lipid Microbiology, DOI 10.1007/978-3-540-77587-4_154, # Springer-Verlag Berlin Heidelberg, 2010
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Microorganisms Utilizing Sulfur-Containing Hydrocarbons
Abstract: Bacteria which are able to transform sulfur-containing compounds, for utilization of either the sulfur or the carbon skeleton, are widely spread in nature. In this chapter, we focus on those bacteria able to degrade heterocyclic hydrocarbons by extracting the sulfur atom without major disruption of the hydrocarbon moiety. Benzothiophene and dibenzothiophene are present in crude oil, and have been utilized as models of thiocyclic sulfur-containing species present in real fractions. These compounds are difficult to desulfurize through conventional desulfurization processes. Here we present information on the desulfurization of these sulfur heterocyles by bacteria. The different metabolic pathways are described with emphasis on the 4S pathway, including the genes and enzymes involved. Research opportunities are identified and novel approaches to deepen our comprehension of these metabolic pathways are proposed.
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Introduction
Sulfur is the most abundant heteroatom in petroleum and is distributed in all three phases. In natural gas, sulfur content may be as high as 5% wt, present mainly as H2S, volatile organic sulfides and thiols. Light oil may contain 0.5% sulfur whereas in heavy oil the content may be up to 6%. Solid petroleum or asphalt, may also contain up to 6% sulfur, as part of molecules that are among the most recalcitrant in nature. Sulfur is unevenly distributed through the crude oil distillation fractions in the form of heterocyclic thiophenic compounds, concentrating in the highest boiling point fractions (> Fig. 1). Other organic sulfur compounds are present in light oil fractions as mercaptans as well as organic mono-
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