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排序方式: 共有2045条查询结果,搜索用时 15 毫秒
1.
Caterina Dinnella Gaetano Lanzarini Andrea Stagni Claudio Palleschi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(3):237-241
Endopectinlyase (EC 4.2.2.10) from Aspergillus japonicus was immobilized on to γ-alumina. Adsorption performed at pH 5·0 and a subsequent cross-linking phase using 0·1% glutaraldehyde were the chosen immobilization conditions. The comparison between the main biochemical parameters of the immobilized and free form of the enzyme showed that the immobilization procedure used did not affect the enzyme biochemical properties. The interactions between the carrier and the enzyme are essentially secondary bonding. In fact they depend on the pH and on the presence of phosphate ions in the medium. A tentative chemical model of the biocatalytic matrix thus obtained is proposed. 相似文献
2.
Immobilization was carried out of the lactate dehydrogenase (LDH) from rabbit muscle (EC 1.1.1.27), cross-linked through the bifunctional reactive glutar-aldehyde on to nylon tubing (1 m long, 53cm2 internal surface area). Immobilized LDH inactivation kinetics are of first order (t1/2 = 3·6 years, k = 5·4,e?4 day?1 to 5°C). The smaller effect of pH on activity than in the case of LDH in solution can be explained on the basis of limitation to proton diffusion towards the support. A limiting effect to free external diffusion of the substrate towards and products from the support was also observed, an effect which seems to determine the effective kinetic behaviour of immobilized LDH. The apparent optimum temperature is centred around 40°C, observing a clear inactivation (thermal denaturation) above this temperature. In the temperature range studied (10–40°C), the co-existence was seen of a kinetic control accompanied by another control, involving diffusional transport of substrates and products, on the global activity of the immobilized enzyme. This makes the Arrhenius profiles curvilinear. Both graphic and statistical non-linear regression analysis of the kinetic data—rate, v, versus substrate concentration [S]—carried out under conditions in which the diffusional limitations can be considered negligible (high recirculation flow rate), permitted investigation of the intrinsic kinetic behaviour of immobilized LDH. In this sense, it can be deduced that the rate equation to which these data seem to be fitted is of the polynomial quotient type in [S] of minimum degree 2:2. Although the diffusional limitations have a marked effect on the type of global kinetics shown by immobilized LDH, temperature was not found to affect its v[S] behaviour. The experimental evidence obtained thus indicates that the rate equation in the 10-40°C temperature range continues to be a rational equation of at least degree 2:2 in [S]. 相似文献
3.
Sandra Aparecida de Assis Pedro Fernandes Bruno Sommer Ferreira Joaquim MS Cabral Olga Maria Mascarenhas Faria Oliveira 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(3):277-280
A partially purified extract of pectinmethylesterase (PME) from acerola fruit was immobilized on various supports: glass, celite, chrysotile, agarose, concanavalin A Sepharose 4B, egg shell, polyacrylamide and gelatin. In addition, reticulation with glutaraldehyde was assessed, as well as the use of gelatin in the presence of celite, glass and silica. The highest immobilization yields were obtained when the pectinmethylesterase was immobilized in concanavalin A Sepharose 4B (81.7%) and in gelatin‐water (78.0%). Copyright © 2004 Society of Chemical Industry 相似文献
4.
κ‐Carrageenan hydrogel crosslinked with protonated polyethyleneimine (PEI+) and glutaraldehyde (GA) was prepared and evaluated as a novel biocatalytic support for covalent immobilization of penicillin G acylase (PGA). The method of modification of the carrageenan biopolymer is clearly illustrated using a schematic diagram and was verified by FTIR, elemental analysis, DSC, and INSTRON using the compression mode. Results showed that the gels' mechanical strength was greatly enhanced from 3.9 kg/cm2 to 16.8 kg/cm2 with an outstanding improvement in the gels thermal stability. It was proven that, the control gels were completely dissolved at 35°C, whereas the modified gels remained intact at 90°C. The DSC thermogram revealed a shift in the endothermic band of water from 62 to 93°C showing more gel‐crosslinking. FTIR revealed the presence of the new functionality, aldehydic carbonyl group, at 1710 cm?1 for covalent PGA immobilization. PGA was successfully immobilized as a model industrial enzyme retaining 71% of its activity. The enzyme loading increased from 2.2 U/g (control gel) to 10 U/g using the covalent technique. The operational stability showed no loss of activity after 20 cycles. The present support could be a good candidate for the immobilization of industrial enzymes rich in amino groups, especially the thermophilic ones. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
5.
Y. Murat Elin Mehmet Saak 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(2):174-180
This paper presents the results of urease immobilization onto methacrylic acid–acrylamide grafted poly(ethyleneterephthalate) fibres. The graft yield strongly affected the maximum activity of the immobilized enzyme up to a value of 70·2%. Higher grafting caused a decline in urease activity and led to the degradation of the fibres. The minor changes observed in Km and Vmax demonstrated that the conformational changes existed during immobilization were not extensive. However, 70·2% methacrylic acid–acrylamide-g-fibres containing urease were more stable towards acidic and alkaline pH, high temperature and storage conditions compared with free enzyme. Apart from the increase in stability to heat inactivation, the initial enzymatic activity of the urease–fibre system remained almost unchanged even after 40 repeated assays corresponding to 10 h of operation in 4 months, indicating the excellent durability of the system. 相似文献
6.
A simulation model for winter wheat growth, crop nitrogen dynamics and soil nitrogen supply was tested against experimental data. When simulations of dry matter production agreed with measurements, nitrogen uptake was simulated accurately. The total amount of soil mineral nitrogen as well as the distribution of mineral nitrogen over the various soil layers were generally simulated well, except for experiments in which fertilizer was applied late in spring. In these experiments, applied nitrogen disappeared because it could not be accounted for by the model. Some explanations for this disappearance are briefly discussed. 相似文献
7.
An easy pot incubation method for measuring nitrogen mineralization from easily decomposable organic material under well defined conditions 总被引:1,自引:0,他引:1
K. Thorup-Kristensen 《Nutrient Cycling in Agroecosystems》1994,38(3):239-247
A pot incubation method for measuring mineralization dynamics from fresh plant material was tested. The aim was to develop a method which under well-defined conditions could produce mineralization data suited for estimating model input parameters for nitrogen prediction models. The results showed that the water tension of the soil could be controlled easily and precisely by diffusion through porous ceramic cups, and that nitrogen mineralization or immobilization could be measured already after 15 days at 15°C. The results showed that for the incubated catch crop residues carbon, nitrogen and nitrate-N contents were the most important factors determining mineralization. No significant effects ould be ascribed to other parameters measured. 相似文献
8.
生化需氧量(BOD)是表征水中有机污染物含量的重要指标,对水质监测和生化过程控制具有重要意义.总结了构成BOD检测系统的各环节,阐述了BOD微生物传感器中微生物选取、固定化以及换能器等关键技术,分析了不同方法的特点,讨论了目前BOD微生物传感器在研究中遇到的主要问题,并对其发展方向进行了展望. 相似文献
9.
10.
产纤维素酶细胞固定化研究 总被引:3,自引:0,他引:3
用海藻酸钙凝胶包埋法制备木霉固定化细胞,研究了固定化条件和培养条件对固定化细胞稳定性及产纤维素酶的影响,初步确定了产纤维素酶木霉细胞的固定化方法。 相似文献