Desulfurization of model and diesel oils by resting cells of Gordona sp.

The desulfurization activity of the resting cells of Gordona sp. CYKS1 was strongly depended on harvest time and the highest value when the cells had been harvested in the early growth phase (0.12 mg sulfur g^–1 cell^–1 h^–1). For the model oil, hexadecane containing dibenzothiophene, the specific desulfurization rate decreased as the reaction proceeded. Both the specific and the volumetric desulfurization rates were not significantly affected by the aqueous-to-oil phase ratio. The diesel oils, light gas oil and a middle distillate unit feed were desulfurized at higher rates (ca. 0.34 mg sulfur g^–1 cell^–1 h^–1) than the model oil (0.12 mg sulfur g^–1 cell^–1 h^–1).     

Modulation of cytokeratin expression during in vitro cultivation of human hepatic stellate cells: evidence of transdifferentiation from epithelial to mesenchymal phenotype

The embryonal origin of hepatic stellate cells (HSCs), the principal cells in hepatic fibrogenesis, is still intriguing. To explore the origin and the differentiation of HSCs, we studied the expression of cytokeratin 18 (CK18) and 19 (CK19), the standard markers of simple epithelial cells, in cultured human HSCs. Hepatic stellate cells were isolated from five normal human livers. In immunofluorescence staining, both clone C-51 anti-CK18 antibody and clone RCK108 anti-CK19 antibody labeled almost all stellate cells in the primary culture. Double immunofluorescence staining for cytokeratin/vimentin and cytokeratin/alpha-smooth muscle actin detected by confocal laser scanning microscopy clearly demonstrated the localization of cytokeratin immunoreactivity in human HSCs. During subsequent cultivation of human HSCs to the tenth passage, immunocytochemical staining and western blot analysis demonstrated gradually decreasing profiles of CK18 and CK19 expression. The progressive reduction of cytokeratin expression was further confirmed in a culture of clone cells originated from a single HSC. In conclusion, both CK18 and CK19 are expressed in cultured human HSCs, and the extent of their expression decreases gradually during prolonged cultivation. Our results suggest that HSCs may be of epithelial origin, and that they undergo the transdifferentiation from epithelial to mesenchymal phenotype during an activation process in vitro.     

Degradation of polyaromatic hydrocarbons by Burkholderia cepacia 2A-12

A new strain of bacterium degrading polyaromatic hydrocarbons (PAHs), Burkholderia cepacia 2A-12, was isolated from oil-contaminated soil. Of three PAHs, the isolated strain could utilize naphthalene (Nap) and phenanthrene (Phe) as a sole carbon source but not pyrene (Pyr). However, the strain could degrade Pyr when a cosubstrate such as yeast extract (YE) was supplemented. The PAH degradation rate of the strain was enhanced by the addition of other organic materials such as YE, peptone, glucose, and sucrose. YE was a particularly effective additive in stimulating cell growth as well as PAH degradation. When 1 g YE l^–1, an optimum concentration, was supplemented into the basal salt medium (BSM) with 215 mg Phe l^–1, the specific growth rate (0.30 h^–1) and Phe-degrading rate (29.6 mol l^–1 h^–1) were enhanced approximately ten and three times more than those obtained in the BSM with 215 mg Phe l^–1, respectively. Both cell growth and PAH degradation rates were increased with increasing Phe and Pyr concentrations, and B. cepacia 2A-12 had a tolerance against Phe and Pyr toxicity at the high concentration of 730–760 mg l^–1. Through kinetic analysis, the maximum specific growth rate ( _max) and PAH degrading rate ( _max) for Phe were obtained as 0.39 h^–1 and 300 mol l^–1 h^–1, respectively. Also, _max and _max for Pyr were 0.27 h^–1 and 52 mol l^–1 h^–1, respectively. B. cepacia 2A-12 could simultaneously degrade crude oil as well as PAHs, indicating that this bacterium is very useful for the removal of oils and PAHs contaminants.     

Rhizoremediation of diesel-contaminated soil using the plant growth-promoting rhizobacterium <Emphasis Type="Italic">Gordonia</Emphasis> sp. S2RP-17

A plant growth-promoting rhizobacterium (PGPR) was isolated and identified as Gordonia sp. S2RP-17, which showed ACC deaminase and siderophore synthesizing activities. Its maximum specific growth rate was 0.54 ± 0.12 d⁻¹ at 5,000 mg L⁻¹ of total petroleum hydrocarbon (TPH), and its maximum diesel degradation rate was 2,434.0 ± 124.4 mg L⁻¹ d⁻¹ at 20,000 mg L⁻¹ of TPH. The growth of Zea mays was significantly promoted by the inoculation of Gordonia sp. S2RP-17 in the diesel-contaminated soil. Measured TPH removal efficiencies by various means were 13% by natural attenuation, 84.5% by planting Zea mays, and 95.8% by the combination of Zea mays and Gordonia sp. S2RP-17. The S2RP-17 cell counts were maintained at 1 × 10⁶ CFU g-soil⁻¹ during the remediation period, although they slightly decreased from their initial numbers (2.94 × 10⁷ CFU g-soil⁻¹). These results indicate that rhizoremediation using both Zea mays and Gordonia sp. S2RP-17 is a promising strategy for enhancing remediation efficiency of diesel-contaminated soils.     

Biocatalytic desulfurization of diesel oil in an air-lift reactor with immobilized Gordonia nitida CYKS1 cells

A new type of air-lift reactor with immobilized Gordonia nitida CYKS1 cells on a fibrous support was designed and used for the biocatalytic desulfurization (BDS) of diesel oil. Its performance was evaluated at different phase ratios of the oil to the aqueous medium (or oil phase fractions) and different sucrose concentrations. When the reaction mixture contained 10% diesel oil (v/v), 61-67% of sulfur was removed as the sulfur content decreased from 202-250 to 76-90 mg L(-1) in 72 h. The sulfur content did not decrease any further because the remaining sulfur compounds were recalcitrant to BDS. During the desulfurization, the strain CYKS1 consumed hydrocarbons in the diesel oil, mainly n-alkanes with 10-26 carbons, as carbon source even though an easily available carbon source, sucrose, was supplied.     

In the limb AER Bmp2 and Bmp4 are required for dorsal-ventral patterning and interdigital cell death but not limb outgrowth

The apical ectodermal ridge (AER) in the vertebrate limb is required for limb outgrowth and patterning. To investigate the role BMP ligands expressed in the AER play in limb development we selectively inactivated both Bmp2 and Bmp4 in this tissue. The autopods of mice lacking both of these genes contained extra digits, digit bifurcations and interdigital webbing due to a decrease in programmed cell death and an increase in cell proliferation in the underlying mesoderm. Upon removal of Bmp2 and Bmp4 in the AER, no defects in proximal-distal patterning were observed. At the molecular level, removal of Bmp2 and Bmp4 in the AER caused an increase in Fgf expression, which correlated with an increase in both the width and length of the AER. Investigation of Engrailed-1 (En1) expression in the AER of limb buds in which Bmp2 and Bmp4 had been removed indicated that En1 expression was absent from this tissue. Our data suggests that AER expression of Bmp2 and Bmp4 is required for digit and dorsal-ventral patterning but surprisingly not for limb outgrowth.     

Tobermolite effects on methane removal activity and microbial community of a lab-scale soil biocover

Three identical lab-scale biocovers were packed with an engineered soil (BC 1), tobermolite only (BC 2), and a mixture of the soil and tobermolite (BC 3), and were operated at an inlet load of 338–400 g-CH₄ m^?2 d^?1 and a space velocity of 0.12 h^?1. The methane removal capacity was 293 ± 47 g-CH₄ m^?2 d^?1 in steady state in the BC 3, which was significantly higher than those in the BC 1 and BC 2 (106 ± 24 and 114 ± 48 g-CH₄ m^?2 d^?1, respectively). Quantitative PCR indicated that bacterial and methanotrophic densities (6.62–6.78 × 10⁷ 16S rDNA gene copy number g-dry sample^?1 and 1.37–2.23 × 10⁷ pmoA gene copy number g-dry sample^?1 in the BC 1 and BC 3, respectively) were significantly higher than those in the BC 2. Ribosomal tag pyrosequencing showed that methanotrophs comprised approximately 60 % of the bacterial community in the BC 2 and BC 3, while they only comprised 43 % in the BC 1. The engineered soil favored the growth of total bacteria including methanotrophs, while the presence of tobermolite enhanced the relative abundance of methanotrophs, resulting in an improved habitat for methanotrophs as well as greater methane mitigation performance in the mixture. Moreover, a batch experiment indicated that the soil and tobermolite mixture could display a stable methane oxidation level over wide temperature (20–40 °C, at least 38 μmol g-dry sample^?1 h^?1) and pH (5–8, at least 61 μmol g-dry sample^?1 h^?1) ranges. In conclusion, the soil and tobermolite mixture is promising for methane mitigation.     

Two-stage biogas production by co-digesting molasses wastewater and sewage sludge

We evaluated the feasibility of co-digesting molasses wastewater and sewage sludge in a two-stage hydrogen- and methane-producing system. The highest energy was recovered at the 21-h hydraulic retention time (HRT) of the first hydrogenic reactor and at 56-h HRT of the secondary methanogenic reactor. Hence, the two-stage system recovered 1,822 kJ from 1 L of the mixed wastes (19.7: hydrogenic reactor plus, 1,802 kJ L^?1: methanogenic reactor). Despite the overloaded VFA-run with a short HRT of 56 h, the GAC-CH₄ reactor increased methane production rate and yields due to enhanced pH buffer capacity. An RNA-based community analysis showed that the Ethanoligenens and Methanosaeta dominated the hydrogen and methane bioreactor, respectively. The two-stage system of co-digesting molasses and sewage sludge is particularly cost-effective due to non-pretreatment of sewage sludge.     

Some characteristics of cytochromec-555 isolated from sulfide oxidizingXanthomonas sp. DY44

From a heterotrophic bacterium,Xanthomonas sp. DY44 which was previously reported to oxidize hydrogen sulfide (H₂S) to polysulfide, cytochromec-555 (cyt.c-555) responsible for oxidation of sulfide was purified by DEAE-Toyopearl and Sepadex G-75 column chromatography. Cyt.c-555 with a molecular weight of 12,500 showed maximum absorption at 555 nm (α-peak), 522 nm (β-peak) and 417 nm (γ-peak) for the reduced form which was prepared by addition of Na₂S₂O₄. Cyt.c-555 was also reduced by addition of sulfide (Na₂S and H₂S), and the oxidized products of sulfide by cyt.c-555 was identified as polysulfide. The reduced form of cyt.c-555 was suggested to be oxidized coupled with cyt.c oxidase which is tolerant to sulfide.