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1.
The catalase (fromAspergillus niger) has been immobilized by a chemical method on the pous SiO2 modified with γ-aminopropyltrietoxysilane, followed with glutaraldehyde and by a physical method in alginate and γ-carrageenan
gel. Optimum support:enzyme ratios and pH values were determined for modified SiO2 in a series of immobilization reactions of catalase in the presence of the crosslinking agent glutaraldehyde, and for alginate
and γ-carrageenan in the presence of hemoglobin and bovine serum albimine. pH and temperaturedependent activity variations
and the stability properties of immobilized catalase preparations were investigated. Rate constants for H2O2 decomposition and catalase deactivation were determined. The decomposition rate of H2O2 used in the cold pasteurizatioan of milk were investigated in a discontinuous batch type reactor system. Activity half-lives
of immobilized catalase were determined. 相似文献
2.
The alterations of organic acids citrate, α-ketoglutarate, succinate, fumarate, malate production together with isocitrate
lyase activity as a glyoxalate shunt enzyme, and antibiotic production of Streptomyces sp M4018 were investigated in relation to changes in the glucose, glycerol and starch concentrations (5–20 g/L) after identification
as a strain of Streptomyces hiroshimensis based on phenotypic and genotypic characteristics. The highest intracellular citrate and α-ketoglutarate levels in 20 g/l
of glucose, glycerol, and starch mediums were 399.47 ± 4.78, 426.93 ± 6.40, 355.84 ± 5.38 ppm and 444.81 ± 5.12, 192.96 ± 2.26,
115.20 ± 2.87 ppm, respectively. The highest succinate, malate, and fumarate levels were also determined in 20 g/l of glucose
medium as 548.9 ± 11.21, 596.15 ± 8.26, and 406.42 ± 6.59 ppm and the levels were significantly higher than the levels in
glycerol and starch. Extracellular organic acid levels measured also showed significant correlation with carbon source concentrations
by showing negative correlation with pH levels of the growth medium. The antibiotic production of Streptomyces sp. M4018 was also higher in glucose medium as was the case also for organic acids when compared with glycerol. On the other
hand, there is no production in starch. 相似文献
3.
Phenylalanine dehydrogenase (l-PheDH) from Sporosarcina ureae was immobilized on DEAE-cellulose, modified initially with 2-amino-4,6-dichloro-s-triazine followed by hexamethylenediamine
and glutaraldehyde. The highest activity of immobilized PheDH was determined as 95.75 U/g support with 56% retained activity.
The optimum pH value of immobilized l-PheDH was shifted from pH 10.4 to 11.0. The immobilized l-PheDH showed activity variations close to the maximum value in a wider temperature range of 45–55 °C, whereas it was 40 °C
for the native enzyme. The pH and the thermal stability of the immobilized l-PheDH were also better than the native enzyme. At pH 10.4 and 25 °C, K
m values of the native and the immobilized l-PheDH were determined as K
m Phe = 0.118, 0.063 mM and K
m NAD+ = 0.234, 0.128 mM, respectively. Formed NADH at the exit of packed bed reactor column was detected by the flow-injection
analysis system. The conversion efficiency of the reactor was found to be 100% in the range of 5–600 μM Phe at 9 mM NAD+ with a total flow rate of 0.1 mL/min. The reactor was used for the analyses of 30 samples each for 3 h per day. The half-life
period of the reactor was 15 days. 相似文献
4.
A copper(I)-catalyzed reaction of a variety of 4-aryl-pent-4-enoates with nosyliminoiodane generated in situ provides the corresponding 5-aryl-5-nosylamidomethylbutyrolactones. The reaction presumably proceeds via an aziridine intermediate, which could be isolated in one case. 相似文献
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6.
Carbonyl sulfide (COS), a component of volcanic gas emissions and interstellar gas clouds, is shown to be an efficient condensing agent in the context of phosphate chemistry in aqueous solutions. We report that high-energy aminoacyl-phosphate anhydrides and aminoacyl adenylates are generated in solutions containing amino acids, COS, and the corresponding phosphate molecule. We further show that the mixed anhydrides of amino acids and inorganic phosphate are phosphorylating agents, producing pyrophosphate in better than 30% yield in the presence of Ca2+ precipitates. The amino acid dependent activations of phosphate reported here, which occur in parallel with the production of peptides, suggest that these two reactions may have shared a common intermediate on the prebiotic Earth. 相似文献
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9.
Leman Tarhan 《Applied biochemistry and biotechnology》1991,31(2):109-117
Polyvinylalcohol crosslinked with terephthaldicarboxaldehyde and was modified with 2-amino-4,6-dichloro-s-triazine. Optimum
conditions for immobilization of catalase on modified and gelatine-coated modified polyvinylalcohol were investigated. Activity
variations with respect to pH, temperature, stability behavior, andk
m(appl) values were investigated for the native and immobilized catalases. Rate constants for H2O2 decomposition and for inactivation of immobilized catalase were determined using a discontinuous batch-type reactor. The
influence of H2O2 concentration on the catalase inactivation was investigated. 相似文献
10.
A palladium-catalysed reaction of conjugated enyne oxiranes with organoboron reagents is described. This method allows aryl-substituted vinylallenes containing a hydroxyl group on the allylic position to be synthesized, with good diastereomeric ratios, under mild conditions. 相似文献