[17]P4 Selective Microbial Desulfurization of Petroleum Fractions

[17]P4 Selective Microbial Desulfurization of Petroleum Fractions

A bacterial strain able to operate the oxidative cleavage of the C-S bond has been isolated in Eniricerche laboratories. The strain was obtained from a soil formerly contaminated by a heavy crude oil at high content of Sulfur which was cleaned up by bioremediation. Taxonomic analysis allowed to classify the bacterium as belonging to Arthrobacter genus. The culture was named DS7 and was deposited at CBS (Baarn, The Netherlands). The isolate can utilize different organosulfur compounds as a source of Sulfur (benzo and dibenzothiophene

1,2-benzonaphthothiophene and thianthrene). Precultivated cells desulfurize thiophene, dibenzothiophene and their C,-C, alkyl substitutes according to the 4-S pathway. Genetic analysis demonstrated that the desulfurization trait is encoded on a plasmid. Enzymes responsible for desulfurization are encoded by genes having the same sequence of different strains mentioned in the literature (Rhodococcus rodochrous). Desulfurization takes place in model systems (dibenzothiophene in hydroalcoholic solutions and in C,-C, n-alkanes) as well as in gasoline, diesel oil, kerosene and fuel oil. Heavy metals usually contained in crude oils scarcely affect the desulfurization activity of DS7. On the contrary, the activity is reduced by volatile hydrocarbons such as benzene, toluene and pentane. DS7 is a surfactant producer strain and it can be used in oil-water systems without addition of emulsifiers. A conceptual diagram for the desulfurization of petroleum derivatives based on the specific properties of DS7 has been submitted for patent application.The 4-S pathway is generally accepted as the most interesting mechanism for the removal of Sulfur from organic molecules contained in fossil fuels. It allows in fact the specific release of Sulfur, leaving unchanged the fuel heating value. However, only a few bacteria are able to operate according to this pathway, namely: (i) Rhodococcus erythropolis', Arthrobacter parafineus', Bacillus sphaericus and Rhodococcus rhodochrous3. The last one, currently known as IGTS-8, is presently under deep investigation on pilot scale4. In this work the relevant performances of a new strain of Arthrobacter sp., recently isolated in Eniricerche able to operate according the 4-S pathway are presented.The strain was taminated by a EXP ER I M E NTAL Bacterial growth obtained from a soil formerly conheavy crude oil at high content of Sulfur, which was cleaned up by bioremediation. The isolate was cultivated in 2 liters flasks using a substrate containing nutrients and microelements and (per liter): dibenzothiophene (DBT) 0.5 g, succinic acid 4.0 g. The flasks were incubated at 30°C under mild stirring (initial pH = 6.4 by NaOH addition).The

1997-10-12

Daddario, E.

Fasc, L.

Gianna, R.

Serbolisca, L.

Robertiello, A.

conferencePaper

I562WJ9Q