Naphtho[2,1-b]thiophene (NTH) is an asymmetric structural isomer of dibenzothiophene (DBT), and in addition to DBT derivatives, NTH derivatives can also be detected in diesel oil following hydrodesulfurization treatment. Rhodococcus sp. strain WU-K2R was newly isolated from soil for its ability to grow in a medium with NTH as the sole source of sulfur, and growing cells of WU-K2R degraded 0.27 mM NTH within 7 days. WU-K2R could also grow in the medium with NTH sulfone, benzothiophene (BTH), 3-methyl-BTH, or 5-methyl-BTH as the sole source of sulfur but could not utilize DBT, DBT sulfone, or 4,6-dimethyl-DBT. On the other hand, WU-K2R did not utilize NTH or BTH as the sole source of carbon. By gas chromatography-mass spectrometry analysis, desulfurized NTH metabolites were identified as NTH sulfone, 2-hydroxynaphthylethene, and naphtho Sulfur oxides generated by combustion of fossil fuel lead to acid rain and air pollution. Therefore, today petroleum is treated by hydrodesulfurization (HDS) using metallic catalysts in the presence of hydrogen gas under extremely high temperature and pressure. Although HDS can remove various types of sulfur compounds, some types of heterocyclic sulfur compounds cannot be removed. Dibenzothiophene (DBT) is one such recalcitrant organosulfur compound and is widely recognized as a model target compound for deeper desulfurization, since DBT derivatives can be detected in diesel oil following HDS treatment. Therefore, the application of a biodesulfurization process using a DBT-desulfurizing microorganism following HDS, mainly for diesel oil, has attracted attention for achievement of deeper desulfurization (16,20). Some mesophilic and thermophilic DBT-desulfurizing microorganisms have been isolated, for example, Rhodococcus sp. strain IGTS8 (1, 4, 21, 22), Rhodococcus erythropolis D-1 (8), R. erythropolis H-2 (17, 18), R. erythropolis KA2-5-1 (6), and Paenibacillus sp. strain A11-2, which desulfurizes DBT at 60°C (7, 11). We have also isolated Bacillus subtilis WU-S2B (9) and Mycobacterium phlei WU-F1 (2), which could desulfurize DBT and its derivatives over a wide temperature range of 20 to 50°C and at the highest level at 45 to 50°C. These bacteria desulfurize DBT through the sulfur-specific degradation pathway with the selective cleavage of carbon-sulfur (C-S) bonds without reducing the energy content (4,21,22). Naphtho[2,1-b]thiophene (NTH) (see Fig. 3B), which includes a benzothiophene (BTH) (see Fig. 3A) structure, is an asymmetric structural isomer of DBT. Recently it has become apparent that in addition to DBT derivatives, NTH derivatives can also be detected in diesel oil following HDS treatment, although NTH derivatives are minor components in comparison with DBT derivatives (unpublished data). Therefore, NTH may also be a model target compound for deeper desulfurization. Kropp et al. (13) have reported that Pseudomonas sp. strain W1 could degrade NTH. However, this bacterium utilized NTH as the carbon source with reducing the energy content, and the sulfur atom was not remo...
Crystallographic aspects of zinc electrodeposited on to polycrystalline cathode from ZnSO4+H2SO4+H2O baths with or without organic colloids have been investigated by electron diffraction (reflection method) and electron microscopy (replica method). At the initial stage of deposition, the zinc layer always consists of fine‐grained crystallites oriented at random. As the zinc layer becomes thicker, some of these crystallites grow larger to yield a fiber orientation depending on the depositing condition. For such relatively thick zinc layers deposited under various degrees of influence of hydrogen and/or organic colloids, the orientation and texture are interpreted from standpoint of crystal growth.
In order t() throw light upon the nature of stacking fault in i)recipitated cadmium sulphide, the crystals i)rccipitated in epitaxial orientation ozt to tile galena cleavage face are investigated by means of the electron diffraction reflcxion method. It was reported already (Sat(), 1959) that the structure of the precipitate is determined mainly by the composition of the aqueous solution of cadmium salt, from which the crystal is precipitate(t. In the present study, intensity distributions in diffraction patterns of many precipitates obtained with various ca(hnium salt solutions are dealt with in detail. The conchtsions are (1) that the stacking faults observe(t in l)recipitated cadmium sulphide are 'growth faults', (2) that tho 'Reiehweite' of the growth necessary and sufficient for interpretation of the experim(mtal results is 3, and (3) that the 'growth faults' in precipitated cadmium suli)hide arise invariably in such a way that the faulty sequences, hcx.-~ cub. and cub. -, hex., are comparatively rare.
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