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191.
192.
Koike Y Cai HJ Higashiyama K Fujikawa S Park EY 《Journal of Bioscience and Bioengineering》2001,91(4):382-389
The influence of the consumed carbon to nitrogen (C/N) ratio on arachidonic acid (AA) production and mycelial morphology was investigated in cultures of Mortierella alpina using shake flasks and a fermentor. The consumed C/N ratio was varied from 5 to 32 under the condition that the total initial amount of carbon and nitrogen sources was 50 g/l. Cellular yield increased markedly at C/N ratios below 7; carbon utilization was switched from cellular growth to lipid biosynthesis in the C/N ratio range of 7-15; lipid biosynthesis was most active when the C/N ratio was in the range of 15-32. However, for C/N ratios higher than 15, the mycelial concentration decreased due to nitrogen limitation but the lipid yield still increased. In the presence of excess nitrogen, the biomass concentration depended on the amount of the nitrogen source, but the AA yield was inversely related to this. On the other hand, in the presence of excess carbon, the fatty acid concentration increased with carbon source concentration but the AA concentration remained constant. From the viewpoint of AA production, the optimum C/N ratio was in the range of 15 to 20 with a balance between the amounts of carbon and nitrogen sources. When an enriched medium was used at a fixed C/N ratio of 20, the cellular and AA concentrations were shown to be proportional to the total concentrations of carbon and nitrogen sources in both flasks and the fermentor. The whole pellet size and width of pellet annular regions did not change with increasing C/N ratio for C/N ratios below 20 in the flask cultures. However, when the C/N ratio was higher than 20, these sizes increased in proportion to the C/N ratio. 相似文献
193.
194.
Shin-Ichi Ito Tatsushi Fujimori Ken Nagashima Koichi Yuzaki Kimio Kunimori 《Catalysis Today》2000,57(3-4):247-254
The extent of Rh–niobia interaction in niobia-supported Rh (Rh/Nb2O5), niobia-promoted Rh/SiO2 (Nb2O5–Rh/SiO2) and RhNbO4/SiO2 catalyst after H2 reduction has been investigated by H2 and CO chemisorption measurements. These catalysts have been applied to selective CO oxidation in H2 (CO+H2+O2) and CO hydrogenation (CO+H2), and the results are compared with those of unpromoted Rh/SiO2 catalysts. It has been found that niobia (NbOx) increases the activity and selectivity for both the reactions. 相似文献
195.
Koichi Yuzaki Takayoshi Yarimizu Kenji Aoyagi Shin-ichi Ito Kimio Kunimori 《Catalysis Today》1998,45(1-4):129-134
The study of catalytic decomposition of nitrous oxide to nitrogen and oxygen over Rh catalysts supported on various supports (USY, NaY, Al2O3, ZrO2, FSM-16, CeO2, La2O3) showed that the activities of Rh/Al2O3 and Rh/USY (ultrastable Y zeolite) catalysts were comparable to or higher than the other catalysts reported in the literatures. The catalytic activity of N2O decomposition was sensitive not only to the Rh dispersion but also to the preparation variables such as the Rh precursors and the supports used. A pulsed N2O experiment over a Rh/USY catalyst suggested that the catalytic N2O decomposition occurs on oxygen-covered surface and that O2 may be freed on collision of N2O molecules with the adsorbed oxygen atoms. 相似文献