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Rhodobacter sphaeroides mutants which accumulate 5-aminolevulinic acid under aerobic and dark conditions 总被引:2,自引:0,他引:2
Nishikawa S Watanabe K Tanaka T Miyachi N Hotta Y Murooka Y 《Journal of Bioscience and Bioengineering》1999,87(6):798-804
The photosynthetic bacterium Rhodobacter sphaeroides accumulates 5-aminolevulinic acid (ALA), which is a precursor in tetrapyrrole biosynthesis, under light illumination and upon addition of levulinic acid as an inhibitor of ALA dehydratase. To generate an industrial strain which produces ALA in the absence of light, we sequentially mutated R. sphaeroides CR-286 using N-methyl-N'-nitro-N-nitrosoguanidine (NTG). The mutant strains were screened by cultivating in the absence of light and assayed for ALA by the Ehrlich reaction in a 96-well microtiter plate. The mutant strain CR-386, derived from R. sphaeroides CR-286, was selected as a mutant that exhibited significant ALA accumulation. While CR-286 required light illumination for ALA production, CR-386 was able to accumulate 1.5 mM ALA in the presence of 50 mM glucose, 60 mM glycine, 15 mM levulinic acid and 1.0% (w/v) yeast extract under conditions of agitation in the absence of light. The mutant strain CR-450, derived from strain CR-386, was selected further as a mutant that exhibited significant ALA accumulation but no accumulation of aminoacetone, analogue of ALA. CR-450 accumulated 3.8 mM ALA under the same conditions. In the presence of 50 mM glucose, 60 mM glycine, 5 mM levulinic acid and 1.0% (w/v) yeast extract, the mutant strain CR-520, derived from strain CR-450, and strain CR-606, derived from strain CR-520, accumulated 8.1 mM and 11.2 mM ALA, respectively. In batch fermentation, the strain CR-606 accumulated 20 mM ALA over 18 h after the addition of glycine, levulinic acid, glucose and yeast extract. 相似文献
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干旱胁迫下外源ALA对烤烟幼苗光合特性和抗氧化能力的影响 总被引:1,自引:0,他引:1
为进一步探究外源5-氨基乙酰丙酸(ALA)对干旱胁迫下烟草幼苗抗旱能力的作用机理,以烤烟品种豫烟10号幼苗为试验材料,采用营养液培养的方法,研究叶面喷施不同浓度的(0~80 mg/L)外源ALA对干旱胁迫下烤烟幼苗烤烟光合特性和抗氧化能力的影响。结果表明干旱胁迫下烤烟叶片细胞活性氧和硫代巴比妥酸(TBARS)含量增加,叶绿体遭到破坏,光合速率降低,植物生长受到抑制。干旱胁迫下外源ALA能够显著降低烤烟叶片活性氧水平,提高抗氧化酶活性,以喷施20 mg/L ALA效果最为显著。其中与PEG处理相比,净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)分别提高96.19%、96.79%和132.43%,抗氧化物酶(SOD、POD、CAT、APX)活性分别提高49.05%,61.97%,64.17%和70.08%。喷施适宜浓度的外源ALA可有效提高烤烟叶片光合特性和抗氧化能力,缓解活性氧伤害,从而增强烤烟幼苗对干旱胁迫的适应能力。 相似文献
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Functional magnetic particles for medical application 总被引:5,自引:0,他引:5
Shinkai M 《Journal of Bioscience and Bioengineering》2002,94(6):606-613
Magnetic particles for medical applications have been developed by many researchers. Since magnetic particles have unique magnetic features not present in other materials, they can be applied to special medical techniques. Separation, immunoassay, magnetic resonance imaging (MRI), drug delivery, and hyperthermia are enhanced by the use of magnetic particles. Magnetite cationic liposomes (MCLs), one of the group of cationic magnetic particles, can be used as carriers to introduce DNA into cells since their positively charged surface associates with the negatively charged DNA. They can also be used as heat mediators for cancer therapy. Magnetic particles conjugated with tumor-specific antibodies have enabled tumor-specific contrast enhancement in MRI. In addition, antibody-conjugated magnetic particles were shown to target renal cell carcinoma cells, and are applicable to the hyperthermic treatment of carcinomas. The use of magnetic particles with their unique features will further improve medical techniques. 相似文献
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介绍了光合细菌的产氢机理,讨论了细菌种类、底物、光等对光合细菌产氢的影响,分析了光合细菌产氢存在的问题和未来的发展趋势. 相似文献
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Watanabe M Kawahara K Sasaki K Noparatnaraporn N 《Journal of Bioscience and Bioengineering》2003,95(4):374-378
We examined the biosorption characteristics of cadmium ions onto a photosynthetic bacterium, Rhodobacter sphaeroides S and a marine photosynthetic bacterium Rhodovulum sp. PS88 in a batch culture system. Both photosynthetic bacteria are capable of cadmium removal with 30 g/l sodium chloride and divalent cations (Mg2+ and Ca2+) in the culture medium. In particular, the strain PS88 shows a high removal ratio and high specific removal rate of cadmium ions from the culture medium under aerobic-dark (heterotrophic) and anaerobic-light (photoheterotrophic) conditions. The adsorption of cadmium onto strains PS88 and S is dependent on the cadmium concentration, and follows the Freundlich adsorption isotherm. In addition, biosorption isotherms for cadmium show that the strain PS88 exhibits higher values of the empirical constant for the cadmium adsorption capacity, Kr, than that of the strain S under both aerobic-dark (K(f)=17.44) and anaerobic-light (K(f)=1.270) conditions. 相似文献
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Alpha-lipoic acid (ALA) is an essential cofactor for mitochondrial multi-enzyme complexes related to energy production. However, it is unstable under light and heat and its biological half-life (t1/2) is short. In this study, ALA was incorporated into alginic acid (Alg) gel beads to achieve stabilisation and sustained release. The cationic polymer chitosan (CS) was also added to the Alg gel beads to better control ALA release. In artificial gastric juice (pH 1.2), ALA release from the Alg gel beads was controlled through simple diffusion from the gel matrix. However, in artificial intestinal juice (pH 6.8), the Alg gel beads were immediately disintegrated. On the other hand, Alg gel beads with CS were not disintegrated in artificial intestinal juice (pH 6.8), and achieved pH-independent sustained release of ALA through an electrostatic interaction between the carboxyl groups of Alg and the amino groups of CS. ALA contained within the Alg gel beads was protected from light (UV) and heat (65 °C) compared with ALA alone. Addition of CS to the Alg gel beads further increased the stability of ALA. Thus, stabilisation and controlled release of ALA was achieved through incorporation of ALA in Alg gel beads containing CS. 相似文献
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