Biodesulfurization of dibenzothiophene by growing cells of Gordonia sp. in batch cultures

A new isolate, identified as Gordonia sp. ZD-7 by 16S rDNA sequence analysis, grew in n-hexadecane containing dibenzothiophene (DBT) which was degraded from 2.8 mM to 0.2 mM within 48 h. Biodesulfurization could be repeatedly performed for more than 190 h, with average desulfurization rates of 5 mmol DBT kg cells (dry wt)⁻¹ h⁻¹.     

Biodesulfurization of dibenzothiophene by recombinant Gordonia alkanivorans RIPI90A

The dszABC genes from newly reported dibenzothiophene biodesulfurizing bacterium, Gordonia alkanivorans RIPI90A were cloned and sequenced. The overall nucleotide sequence similarity between the dszABC genes of G. alkanivorans RIPI90A and those of Rhodococcus erythropolis IGTS8 and Gordonia nitida were 83.1% and 83.2%, respectively. A gene transfer system for G. alkanivorans RIPI90A was established employing the Escherichia coli-Rhodococcus shuttle vector pRSG43 as suitable cloning vector, resulting in transformation efficiencies up to 1.6 x 10(5)CFUs microg(-1) plasmid DNA. This stable vector was applied to cloning and efficient expression of the dsz genes under the control of lac promoter. The recombinant strain was able to desulfurize dibenzothiophene in the presence of inorganic sulfate and sulfur-containing amino acids. The maximum desulfurization activity by recombinant resting cells (131.8 microM2-hydroxybiphenylg(dry cell weight)(-1)h(-1)) was increased 2.67-fold in comparison to the highest desulfurization activity of native resting cells.     

Biodesulfurization of benzothiophene and dibenzothiophene by a newly isolated Rhodococcus strain

Rhodococcus sp. KT462, which can grow on either benzothiophene (BT) or dibenzothiophene (DBT) as the sole source of sulfur, was newly isolated and characterized. GC and GC-MS analyses revealed that strain KT462 has the same BT desulfurization pathway as that reported for Paenibacillus sp. A11-2 and Sinorhizobium sp. KT55. The desulfurized product of DBT produced by this strain, as well as other DBT-desulfurizing bacteria such as R. erythropolis KA2-5-1 and R. erythropolis IGTS8, was 2-hydroxybiphenyl. A resting cells study indicated that this strain was also able to degrade various alkyl derivatives of BT and DBT.     

Biodesulfurization of dibenzothiophene by a newly isolated Rhodococcus erythropolis strain

A new dibenzothiophene (DBT) desulfurizing bacterium was isolated from oil-contaminated soils in Iran. HPLC analysis and PCR-based detection of the presence of the DBT desulfurization genes (dszA, dszB and dszC) indicate that this strain converts DBT to 2-hydroxybiphenyl (2-HBP) via the 4S pathway. The strain, identified as Rhodococcus erythropolis SHT87, can utilize DBT, dibenzothiophene sulfone, thiophene, 2-methylthiophene and dimethylsulfoxide as a sole sulfur source for growth at 30 °C.The maximum specific desulfurization activity of strain SHT87 resting cells in aqueous and biphasic organic–aqueous systems at 30 °C was determined to be 0.36 and 0.47 μmol 2-HBP min⁻¹ (g dry cell)⁻¹, respectively. Three mM DBT was completely metabolized by SHT87 resting cells in the aqueous and biphasic systems within 10 h. The rate and the extent of the desulfurization reaction by strain SHT87 suggest that this strain can be used for the biodesulfurization of diesel oils.     

Biodesulfurization of dibenzothiophene in Escherichia coli is enhanced by expression of a Vibrio harveyi oxidoreductase gene

One possible alternative to current fuel hydrodesulfurization methods is the use of microorganisms to remove sulfur compounds. Biodesulfurization requires much milder processing conditions, gives higher specificity, and does not require molecular hydrogen. In the present work we have produced two compatible plasmids: pDSR3, which allows Escherichia coli to convert dibenzothiophene (DBT) to hydroxybiphenyl (HBP), and pDSR2, which produces a Vibrio harveyi flavin oxidoreductase. We show that the flavin oxidoreductase enhances the rate of DBT removal when co-expressed in vivo with the desulfurization enzymes. The plasmids pDSR2 and pDSR3 were co-expressed in growing cultures. The expression of oxidoreductase caused an increase in the rate of DBT removal but a decrease in the rate of HBP production. The maximum rate of DBT removal was 8 mg/h. g dry cell weight. Experiments were also conducted using resting cells with the addition of various carbon sources. It was found that the addition of glucose or glycerol to cultures with oxidoreductase expression produced the highest DBT removal rate (51 mg/h. g dry cell weight). The culture with acetate and no oxidoreductase expression had the highest level of HBP production. For all carbon sources, the DBT removal rate was faster and the HBP generation rate slower with the expression of the oxidoreductase. Analysis of desulfurization intermediates indicates that the last enzyme in the pathway may be limiting.     

Interaction of fibrinogen with magnetite nanoparticles

The interaction between fibrinogen and magnetite nanoparticles in solution has been studied by the methods of spin labeling, ferromagnetic resonance, dynamic and Rayleigh light scattering. It is shown that protein molecules adsorb on the surface of nanoparticles to form multilayer protein covers. The number of molecules adsorbed on one nanoparticle amounts to ∼65 and the thickness of the adsorption layer amounts to ∼27 nm. Separate nanoparticles with fibrinogen covers (clusters) form aggregates due to interactions of the end D domains of fibrinogen. Under the influence of direct magnetic field, nanoparticles with adsorbed proteins form linear aggregates parallel to the force lines. It is shown that the rate of protein coagulation during the formation of fibrin gel under the action of thrombin on fibrinogen decreases ∼2 times in the presence of magnetite nanoparticles, and the magnitude of the average fiber mass/length ratio grows.     

Biodesulfurization of dibenzothiophene by Gordonia sp. AHV-01 and optimization by using of response surface design procedure

A novel desulfurizing bacterium has been isolated from oil-contaminated soils in Khuzestan. The ability for dibenzothiophene desulfurization and its biochemical pathway were investigated. The bacterium was identified as Gordonia sp. AHV-01 (Genbank Accession No HQ607780) by 16S rRNA gene sequencing. HPLC results and Gibb's assay were shown that dibenzothiophene desulfurized via 4S-pathway Maximum growth (0.426 g dry cells/L) and produced 2-hydroxybiphenyl (63.1 microM) were observed at 120 h of cultivation. By using of response surface design procedure the optimization of pH, temperature and rotary shaker round on the desulfurization reaction of isolate AHV-01 were performed. The optimum conditions were determined at pH of 7.0, temperature of 30 degrees C and rotary shaker round of 180 rpm. At these conditions, the dibenzothiophene desulfurization activity was increased and maximum 2-hydroxybiphenyl production was detected 70.29 microM at 96 h. According to these results, Isolate AHV-01 was capable to desulfurize dibenzothiophene via 4S-pathway and likely it can be useful to reduce organic sulfur contents of crude oil.     

Biodesulfurization of dibenzothiophene and gas oil using a bioreactor containing a catalytic bed with Rhodococcus rhodochrous immobilized on silica

Biodesulfurization (BDS) in a bioreactor packed with a catalytic bed of silica containing immobilized Rhodococcus rhodochrous was studied. Various bed lengths and support particle sizes were evaluated for BDS of dibenzothiophene (DBT) and gas oil. The sulfur-containing substrates were introduced separately into the bioreactor at different feed flows. Higher removal of sulfur from DBT and gas oil was achieved with a long bed, lower substrate flow, and larger sizes of immobilization particles. The packed bed bioreactor containing metabolic active cells was recycled and maintained BDS activity.     

Microbial preparation of metal-substituted magnetite nanoparticles

A microbial process that exploits the ability of iron-reducing microorganisms to produce copious amounts of extra-cellular metal (M)-substituted magnetite nanoparticles using akaganeite and dopants of dissolved form has previously been reported. The objectives of this study were to develop methods for producing M-substituted magnetite nanoparticles with a high rate of metal substitution by biological processes and to identify factors affecting the production of nano-crystals. The thermophilic and psychrotolerant iron-reducing bacteria had the ability to form M-substituted magnetite nano-crystals (M(y)Fe(3-y)O(4)) from a doped precursor, mixed-M iron oxyhydroxide, (M(x)Fe(1-x)OOH, x< or =0.5, M is Mn, Zn, Ni, Co and Cr). Within the range of 0.01< or =x< or =0.3, using the mixed precursor material enabled the microbial synthesis of more heavily substituted magnetite compared to the previous method, in which the precursor was pure akaganeite and the dopants were present as soluble metal salts. The mixed precursor method was especially advantageous in the case of toxic metals such as Cr and Ni. Also this new method increased the production rate and magnetic properties of the product, while improving crystallinity, size control and scalability.     

High-temperature microbial sulfate reduction can be accompanied by magnetite formation

The hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus was found to be capable of lithoautotrophic growth on medium containing molecular hydrogen, sulfate, and amorphous Fe(III) oxide. During the growth of this microorganism, amorphous Fe(III) oxide was transformed into black strongly magnetic sediment rich in magnetite, as shown by Mossbauer studies. Experiments involving inhibition of microbial sulfate reduction and abiotic controls revealed that magnetite production resulted from chemical reactions proceeding at elevated temperatures (83 degrees C) between molecular hydrogen, amorphous Fe(III) oxide, and sulfide formed enzymatically in the course of dissimilatory sulfate reduction. It follows that magnetite production in this system can be characterized as biologically mediated mineralization. This is the first report of magnetite formation as a result of activity of sulfate-reducing microorganisms.     

Dehalogenation of environmental pollutants in microbial electrolysis cells with biogenic palladium nanoparticles

Purpose of work Hydrodehalogenation of persistent pollutants, such as the groundwater contaminants trichloroethylene and diatrizoate, are catalyzed by biogenic Pd nanoparticles. As H₂ gas supply for the dehalogenation reactions is still the limiting factor, this study examines in situ H₂ production in the cathode of a microbial electrolysis cell.     

Biodesulfurization of Dibenzothiophene by Microbial Cells Coated with Magnetite Nanoparticles

Microbial cells of Pseudomonas delafieldii were coated with magnetic Fe₃O₄ nanoparticles and then immobilized by external application of a magnetic field. Magnetic Fe₃O₄ nanoparticles were synthesized by a coprecipitation method followed by modification with ammonium oleate. The surface-modified Fe₃O₄ nanoparticles were monodispersed in an aqueous solution and did not precipitate in over 18 months. Using transmission electron microscopy (TEM), the average size of the magnetic particles was found to be in the range from 10 to 15 nm. TEM cross section analysis of the cells showed further that the Fe₃O₄ nanoparticles were for the most part strongly absorbed by the surfaces of the cells and coated the cells. The coated cells had distinct superparamagnetic properties. The magnetization (δ_s) was 8.39 emu · g⁻¹. The coated cells not only had the same desulfurizing activity as free cells but could also be reused more than five times. Compared to cells immobilized on Celite, the cells coated with Fe₃O₄ nanoparticles had greater desulfurizing activity and operational stability.     

Cyanobacteria and Chlorophyta in situ magnetic harvesting by goethite/magnetite nanoparticles

Journal of Applied Phycology - Separating microalgal cells from the aquatic environment is a crucial step for minimizing their adverse impacts or utilizing microalgal biomass. In this study,...     

Modification of phytochemical production and antioxidant activity of Dracocephalum kotschyi cells by exposure to static magnetic field and magnetite nanoparticles

Plant Cell, Tissue and Organ Culture (PCTOC) - Dracocephlum kotschyi Boiss is a genus in Lamiaceae family and a medicinal herb native to Iran. The cell suspension cultures were treated by static...     

Desulphurization of dibenzothiophene by bacteria

Four out of 187 strains, from enrichment cultures of dibenzothiophene (DBT), grew on DBT or thiophene 2-carboxylate as S sources. The four isolates, presumptively identified as Agrobacterium sp., Xanthomonas sp. and Corynebacterium spp., individually and together desulphurized DBT, producing 2-hydroxybiphenyl and sulphate.M. Constanti and A. Bordons are with the Departament de Bioquímica i Biotecnologia, and J. Giralt is with the Departament d'Enginyeria Química, both of the Universitat Rovira i Virgili, Pl. Imperial Tarraco 1, 43005 Tarragona, Catatonia, Spain     

Desulfurization of dibenzothiophene derivatives by whole cells of Rhodococcus erythropolis H-2

Abstract Transposon mutagenesis was performed to pursue the molecular basis of carbazole catabolic pathway in a carbazple-using bacterium, Pseudomonas sp. CA10. One mutant, TD2, was capable of using anthranilic acid but not carbazole as its sole source of carbon, nitrogen, and energy. Another isolated mutant, designated as TE1, was found to have the opposite ability as TD2. TD2 could not convert carbazole to any other compound under cometabolic conditions. On the other hand, TE1 accumulated catechol and cis,cis -muconate from carbazole. The clone containing Tn 5 -flanking region from TD2, showed the meta -cleavage activity for biphenyl-2,3-diol and analysis of the DNA sequence of this region suggests that the genes involved in the degradation of aromatic compounds are clustered. Our analysis of the DNA sequence of another clone from mutant TE1 showed that the Tn 5 -Mob can be inserted into the homologous catR gene, a gene that reportedly enpodes the positive regulatory protein of the catBC operon. These data suggests that carbazole catabolic pathway comprises at least two different gene clusters (upper pathway and lower pathway) in Pseudomonas sp. CA10.     

Isolation of DNA using magnetic nanoparticles coated with dimercaptosuccinic acid

Lately, the isolation of DNA using magnetic nanoparticles has received increased attention owing to their facile manipulation and low costs. Although methods involving their magnetic separation have been extensively studied, there is currently a need for an efficient technique to isolate DNA for highly sensitive diagnostic applications. We describe herein a method to isolate and purify DNA using biofunctionalized superparamagnetic nanoparticles synthesized by a modified polyol method to obtain the desired monodispersity, followed by surface modification with meso-2,3-dimercaptosuccinic acid (DMSA) containing carboxyl groups for DNA absorption. The DMSA-coated magnetic nanoparticles (DMSA-MNPs) were used for the isolation of DNA, with a maximum yield of 86.16%. In particular, we found that the isolation of DNA using small quantities of DMSA-MNPs was much more efficient than that using commercial microbeads (NucliSENS-easyMAG, BioMérieux). Moreover, the DMSA-MNPs were successfully employed in the isolation of genomic DNA from human blood. In addition, the resulting DNA–nanoparticle complex was directly subjected to PCR amplification without prior elution, which could eventually lead to simple, rapid, sensitive and integrated diagnostic systems.