Desulfurization bacterial

Further research in improving the BDS activity of the biocatalysts was targeted towards the search of co-catalysts and co-factors to enhance overall desulfurization rates as well as promoters to enhance enzyme expression. This research resulted in identification of NADH and FMNH2 as co-factors essential for electron transfer and related oxidoreductase enzymes as co-catalysts as described in detail below. Additionally, other bacterial strains were also investigated as hosts and are reported below. 

Engineered biocatalysts with altered specificity have been developed. A Rhodococcus strain capable of DBT as well as BT desulfurization has been developed by cloning dsz genes into a strain-containing BT desulfurization pathway. The variety of sulfur compounds in petroleum feedstocks and complexity of the problem may require use of a consortium rather than a single bacterial strain. Alternately, use of multiple bioreactors each with a single dominant strain may be employed to achieve maximum desulfurization [299],... 

Abbad-Andaloussi, S. Warzywoda, M., and Monot, F., Microbial desulfurization of diesel oils by selected bacterial strains. Oil Gas Science and Technology-Revue Institut Francais Du Petrole, 2003. 58(4) pp. 505-513. 

Kobayashi, M. Onaka, T. Ishii, Y., et al., Desulfurization of Alkylated Forms of Both Dibenzothiophene and Benzothiophene by a Single Bacterial Strain. Ferns Microbiology Letters, 2000. 187(2) pp. 123-126. 

Wang, P., and Krawiec, S., Desulfurization of Dibenzothiophene to 2-Hydroxybiphenyl by Some Newly Isolated Bacterial Strains. Archives of Microbiology, 1994.161(3) pp. 266-271. 

Hydrocarbon Microbiology biodegradation mechanisms of oil products (gasoline, kerosene, diesel, etc.), pyrolysis, polycyclic aromatic hydrocarbons, chlorinated solvents, and ether fuels refining processes (e.g., oil product microbial desulfurization) and oil production processes (e.g., bacterial corrosion). 

The second patent describes the use of a microbial mixed culture (Hansenula sydowiorum, Hansenula ciferrii, Hansenula lynferdii, and/or Cryptococcus albidus) in coal desulfurization [160], In this process, the raw mined coal is ground to a particle size smaller than 200 mesh forming a slurry with water, at a solids concentration of less than 40wt%. The bacterial cultures are then inoculated into the feedstock slurry. An incubation step is carried out at a temperature near 25°C and at a pH close to neutral. The highest removal achieved was in the range of 46% S removal. 

Results show that the rates of bacterial desulfurization from coal samples are higher in the pipeline loop under turbulent flow conditions as compared to the shake-flask experiments for particle sizes 43 to 20C im. 

Hoffman et al. (18) conducted a parametric study to determine the effect of bacterial strain, N/P molar ratio, the partial pressure of CO2, the coal source and the total reactive surface area on the rate and extent of oxidative dissolution of iron pyrite at a fixed oxygen pressure. The bacterial desulfurization of high pyritic sulfur coal could be achieved in 8 to 12 days for pulp densities upto 20% and particle size of less than 7 um. The most effective strains of T. ferrooxidans were isolated from the natural systems, and the most effective nutrient medium contained low phosphate levels, with an optimal N/P molar ratio of 90 1. 

About 80% pyritic sulfur removal has been achieved by microbial desulfurization of Illinois 6 and Indiana 3 coals using T. ferrooxidans in laboratory shake-flask experiments and in a two-inch pipeline loop. The 10 to 25 wt% coal/water slurry was recirculated at 6-7 ft/sec for 7 to 12 days at 70-90°F. Results also show that the rates of bacterial desulfurization are higher in the pipeline loop under turbulent flow conditions for particle sizes, 43 to 200/m as compared to the shake-flask experiments. It is visualized that the proposed coal slurry pipelines could be used as biological plug flow reactors under aerobic conditions. The laboratory corrosion studies show that use of a corrosion inhibitor will limit the pipeline corrosion rates to acceptable levels. 

Dugan, P.R. and Apel, W.A. 1978. f,Microbial Desulfurization of Coal." In Metallurgical Application of Bacterial Leaching and Related Microbial Phenomenon." Editors, L.E. Murr Torma, A.E. Brieley, J.A. Academic Press, N.Y.pp. 223-250. 

Duarte, G.F., Rosado, A.S., Seldin, L., de Araujo, W. and van Elsas, J.D. (2001) Analysis of bacterial community structure in sulfurous-oil-containing soils and detection of species carrying dibenzothiophene desulfurization (dsz) genes. Applied and Environmental Microbiology, 67, 1052-1062. 

By far the largest fractionation is associated with the bacterial sulfate reduction (see a recent review by Canfield 2001). Dne to the activity of snlfate-redncing bacteria, snch as Desulfovibrio desulfur icons, organic matter is oxidized according to the following equation ... 

Methyl-branched fatty acids are found in lipid fractions of many plants and are very common in bacterial extracts. Sixteen branched fatty acids were produced by different synthetic methods, including alkylation and hydrolysis of oxazolines to obtain 2-alkyl fatty acids. This was achieved through desulfurization of alkyl-substituted thiophenecarboxylic acids for 4- and 6-alkyl fatty acids and the application of the Kolbe reaction of dioic acids to give alkyl branches at different positions of the chain... 

Chandra, D. and Mishra, A.K. 1988. Desulfurization of coal by bacterial means. Resources Conservation and Recycling, 1(3-4) 293-308. 

Sulfur-specific desulfurization of DBTs and other organosulfur compounds is best characterized in the bacterial genus Rhodococcus and exemplified by R. erythropolis strain IGTS8 and involves a series of oxidations of the sulfur moiety followed by a hydrolytic release of sulfite. This and related pathways have been shown to desulfurize a wide range of DBTs, BTHs, and sulfides. Moreover, deep desulfurization to low ppm levels of sulfur has been demonstrated with a variety of hydrotreated diesel range oils. 

Another alternative for the desulfurization of liquid fuels involves biotechnological and biocatalytic processes. These processes are based on bacterial strains, the metabolism of which can convert carbon-rich sulfur compounds. Through a series of enzyme catalytic reactions, the strains remove the sulfur from the hydrocarbon compounds without altering the carbon skeleton [74] (see Figure 34.8). 

The operating conditions, which are easy to manage, make the application of biological processes for the desulfurization of middle distillates advantageous. The process involving the recovery of the bacterial solution does not require the addition of hydrogen or any other consumable. One factor impeding application in fuel cell APUs, however, is the insufficient activity of bacterial strains known to us today. The residence times required would result in unrealistic reactor dimensions. 

Lee et al. studied microbial desulfurization of DBTs bearing alkyl substitutions adjacent to the sulfur atom, such as 4,6-diethyldibenzothiophene (4,6-DEDBT), which are referred to as sterically hindered with regard to access to the sulfur moiety. By using enrichment cultures with 4,6-DEDBT as the sole sulfur source, bacterial isolates which selectively remove sulfur from sterically hindered DBTs were obtained. The isolates were tentatively identified as Artiirobacter species, 1,6-DEDBT sulfone was shown to be an... 

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