Determination of Urinary Glucose by a Flow Injection Analysis Amperometric Biosensor and Ion-Exchange Chromatography

A practical biosensor system has been developed for the determination of urinary glucose using a flow-injection analysis (FIA) amperometric detector and ion-exchange chromatography. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an immobilized enzyme column. On the basis of its negative charge at pH 5.5, endogenous urate in urine samples was effectively retained by an upstream anion-exchange resin column. The biosensor system possessed a sensitivity of 160 ±2.4 RU μM^-1 (RU or relative unit is defined as 2.86 μV at the detection output) for glucose with a minimum detection level of 10 μM. When applied for the determination of urinary glucose, the result obtained compared very well with that of the widely accepted hexokinase assay. The immobilized glucose oxidase could be reused for more than 1000 repeated analyses without losing its original activity. The reuse of the acetate anion-exchange column before replacement would be about 25–30 analyses. Acetaminophen and ascorbic acid were also effectively adsorbed by the acetate anion exchanger. The introduction of this type of anion exchanger thus greatly improved the selectivity of the FIA biosensor system and fostered its applicability for the determination of glucose in urine samples.     

固定化葡萄糖氧化酶活性的X射线微区分析

利用X射线微区分析方法,对固定化活性葡萄糖氧化酶进行了定位分析;葡萄糖作为底物,FeSO4和KI作为捕捉剂,底物经固定化葡萄糖氧化酶催化产生H2O2,后者和捕捉剂反应生成沉淀,可以确定固定化葡萄糖氧化酶的催化活性部位。结果表明：颗粒越小,酶活越高,活性葡萄糖氧化酶在凝胶内分布均匀,且绝大多数葡萄糖氧化酶固定在凝胶的内部。作者还研究了固定化活性葡萄糖氧化酶定位的最佳条件。     

Immobilization of glucose isomerase and its application in continuous production of high fructose syrup

Bilayer glucose isomerase was immobilized in porousp-trimethylaminepolystyrene (TMPS) beads through a molecular deposition technique. Some of the factors that influence the activity of immobilized glucose isomerase were optimized, with the enzyme concentration of 308 IU/mL, enzyme-to-matrix ratio of 924 IU/g wet carrier, and hexamethylene bis(trimethylammonium iodine) concentration of 15 mg/mL giving the maximum catalytic activity (2238 IU/g dry gel) of the immobilized bilayer glucose isomerase, retaining 68.5% of the initially added activity. The half-life of the immobilized bilayer glucose isomerase was approx 45 d at pH 8.5, 60°C, with 50% (w/v) glucose as substrate. The specific productivity of the immobilized bilayer glucose isomerase was 223 g dry D-glucose/g dry immobilized enzyme per d.     

Pigeonpea (Cajanus cajan L.) urease immobilized on glutaraldehyde-activated chitosan beads and its analytical applications

Urease from pigeonpea (Cajanus cajan L.) was covalently linked to crab shell chitosan beads using glutaraldehyde. The optimum immobilization (64% activity) was observed at 4°C, with a protein concentration of 0.24 mg/bead and 3% glutaraldehyde. The immobilized enzyme stored in 0.05 M Trisacetate buffer, pH 7.3, at 4°C had a t _1/2 of 110 d. There was practically no leaching of enzyme (<3%) from the immobilized beads in 30 d. The immobilized urease was used 10 times at an interval of 24 h between each use with 80% residual activity at the end of the period. The chitosan-immobilized urease showed a significantly higher Michaelis constant (8.3 mM) compared to that of the soluble urease (3.0 mM). Its apparent optimum pH also shifted from 7.3 to 8.5. Immobilized urease showed an optimal temperature of 77°C, compared with 47°C for the soluble urease. Time-dependent kinetics of the thermal denaturation of immobilized urease was studied and found to be monophasic in nature compared to biphasic in nature for soluble enzyme. This immobilized urease was used to analyze blood urea of some of the clinical samples from the clinical pathology laboratories. The results compared favorably with those obtained by the various chemical/biochemical methods employed in the clinical pathology laboratories. A column packed with immobilized urease beads was also prepared in a syringe for the regular and continuous monitoring of serum urea concentrations.     

Immobilization on chitosan of a thermophilic βglycosidase expressed inSaccharomyces cerevisiae

ASulfolobus solfataricus β-glycosidase expressed inSaccharomyces cerevisiae (Sβgly) was immobilized on chitosan activated with glutaraldehyde. The yield of immobilization was evaluated as 80%. Compared to the free β-glycosidase, the immobilized enzyme showed a similar pH optimum (pH = 7.0), the same increasing activity up to 80°C, improved thermostability, and no inhibition by glucose. Functional studies pointed out that the kinetic constant values for both enzymes were comparable. A bioreactor, assembled with the immobilized Sβgly, was used for glucose production. The values of cellobiose conversion increased on increasing residence time in the bioreactor, following a nonlinear trend. However, the highest glucose production/ min was obtained at a flow of 0.5 mL/min.     

Immobilization of glucose isomerase and its application in continuous production of high fructose syrup

Bilayer glucose isomerase was immobilized in porousp-trimethylamine-polystyrene (TMPS) beads, through a molecular deposition technique. Some of the factors that influence the activity of immobilized glucose isomerase were optimized, with the enzyme concentration of 308 IU/mL, enzyme:matrix ratio of 924 IU/g wet carrier, and hexamethylenebis(trimethylammonium iodine) concentration of 15 mg/mL, giving the maximum catalytic activity (2238 IU/g dry gel) of the immobilized bilayer glucose isomerase, retaining 68.5% of the initially added activity. The half-life of the immobilized bilayer glucose isomerase was approx 45 d at pH 8.5, 60°C, with 50% (w/v) glucose as substrate. The specific productivity of the immobilized bilayer glucose isomerase was 223 g dry D-glucose/g dry immobilized enzyme per day.     

Immobilization of Xylanase from <Emphasis Type="Italic">Bacillus pumilus</Emphasis> Strain MK001 and its Application in Production of Xylo-oligosaccharides

Xylanase from Bacillus pumilus strain MK001 was immobilized on different matrices following varied immobilization methods. Entrapment using gelatin (GE) (40.0%), physical adsorption on chitin (CH) (35.0%), ionic binding with Q-sepharose (Q-S) (45.0%), and covalent binding with HP-20 beads (42.0%) showed the maximum xylanase immobilization efficiency. The optimum pH of immobilized xylanase shifted up to 1.0 unit (pH 7.0) as compared to free enzyme (pH 6.0). The immobilized xylanase exhibited higher pH stability (up to 28.0%) in the alkaline pH range (7.0–10.0) as compared to free enzyme. Optimum temperature of immobilized xylanase was observed to be 8 °C higher (68.0 °C) than free enzyme (60.0 °C). The free xylanase retained 50.0% activity, whereas xylanase immobilized on HP-20, Q-S, CH, and GE retained 68.0, 64.0, 58.0, and 57.0% residual activity, respectively, after 3 h of incubation at 80.0 °C. The immobilized xylanase registered marginal increase and decrease in K _m and V _max values, respectively, as compared to free enzyme. The immobilized xylanase retained up to 70.0% of its initial hydrolysis activity after seven enzyme reaction cycles. The immobilized xylanase was found to produce higher levels of high-quality xylo-oligosaccharides from birchwood xylan, indicating its potential in the nutraceutical industry.     

Immobilization,characterization, and laboratory-scale application of bovine liver arginase

Arginase isolated from beef liver was covalently attached to a polyacrylamide bead support bearing carboxylic groups activated by a water-soluble carbodiimide. The most favorable carbodiimide wasN-cyclohexyl-Nt’-(methyl-2-p-nitrophenyl-2-oxoethyl) aminopropyl carbodiimide methyl bromide, but for practical purposes,N-cyclohexyl-Nt’-morpholinoethyl carbodiimide methyl tosylate was used. The optimal conditions for the coupling procedure were determined. The catalytic activity of the immobilized arginase was 290–340 U/g solid or 2.9–3.4 U/mL wet gel. The pH optimum for the catalytic activity was pH 9.5, the apparent temperature maximum was at 60°C and K_mapp was calculated to be 0.37M L-arginine. Immobilization markedly improved the conformational stability of arginase. At 60°C, the pH for maximal stability was found to be 8.0. The immobilized arginase was used for the production of L-ornithine and D-arginine.     

多孔壳聚糖膜固定葡萄糖氧化酶活性的X射线微区分析

甲壳素(chitin)是无脊椎动物,特别是节肢动物,如虾、蟹及昆虫等的外骨骼重要组成部分,其学名为β(1,4)-2-乙酰氨基-2-脱氧-D-葡萄糖。壳聚糖是甲壳素脱乙酰基的衍生物,其结构上具有许多—NH2、—OH等反应基团,对蛋白质具有极高的亲和性,且具有生物相容性好、无毒、可生物降解等     

一种基于壳聚糖固定葡萄糖氧化酶的葡萄糖生物传感器的研究

本文选用生物相容性好的壳聚糖作为基体材料，使其与戊二醛交联成网状结构包埋葡萄糖氧化酶制成电化学传感器。这种壳聚糖膜不仅可以减小葡萄糖氧化酶的流失，而且能为酶提供了适宜的微环境。用红外光谱、紫外光谱及透射电镜对膜的形态和性质进行了表征。实验结果表明该传感器具有很快的响应速度，很好的稳定性和重现性，能选择性地催化葡萄糖并测定其浓度。该传感器的制备方法简单，成本低，于冰箱中放置两周信号保持在90％以上，对葡萄糖测量的线性范围为1×10^-5 - 3.4×10^-3mol•L^-1，当信噪比为3:1时检测限为5×10^-6mol•L^-1。     

Immobilization of isolated and cellular hydrogenase ofD. desulfuricans in radiation polymerized polyacrylamides

Purified hydrogenase fromDesulfovibrio desulfuricans was immobilized either by entrapment or absorption onto porous neutral and charged acrylamide beads. Surface absorption and crosslinking on the beads resulted in a high hydrogenase activity and a good immobilization coefficient compared to the enzyme and whole cells entrapped in the same matrix. Maximum enzyme activity (citrate-phosphate buffer) was shifted to pH 6.5 upon immobilization in contrast to 6.0 for the free enzyme and the range of 6–7 for whole cells. Both the purified enzyme and whole cells were most active when held in neutral matrices. Immobilization improved the temperature stability (65‡C) and long term storage (4‡C) of the hydrogenase activity of both the purified enzyme and whole cells.     

Cephalexin synthesis using immobilizedXanthomonas citri cells

For continuous production of cephalexin, whole cells ofXanthomonas citri were immobilized by entrapment in polyacrylamide gel and kappa-carrageenan gel. It wasfound that cells immobilized with kappa-carrageenan showed better thermal stability compared to those immobilized by polyacrylamide gel. The cells immobilized with kappa-carrageenan were treated with glutaraldehyde and hexamethylenediamine to prevent gel destruction during prolonged operation. By immobilizing intact cells, the optimal temperature for the synthetic enzyme reaction shifted higher by 8°C and the optimal pH became broader around 6.2 In continuous operation, the immobilized cells retained better operational stability at 25 than at 37°C, and also showed maximal conversion up to 83% at 25°C.     

Immobilized Fullerene C60‐Enzyme‐Based Electrochemical Glucose Sensor

A mixed‐valence cluster of cobalt(II) hexacyanoferrate and fullerene C60‐enzyme‐based electrochemical glucose sensor was developed. A water insoluble fullerene C60‐glucose oxidase (C60‐GOD) was prepared and applied as an immobilized enzyme on a glassy carbon electrode with cobalt(II) hexacyanoferrate for analysis of glucose. The glucose in 0.1 M KCl/phosphate buffer solution at pH = 6 was measured with an applied electrode potential at 0.0 mV (vs Ag/AgCl reference electrode). The C60‐GOD‐based electrochemical glucose sensor exhibited efficient electro‐catalytic activity toward the liberated hydrogen peroxide and allowed cathodic detection of glucose. The C60‐GOD electrochemical glucose sensor also showed quite good selectivity to glucose with no interference from easily oxidizable biospecies, e.g. uric acid, ascorbic acid, cysteine, tyrosine, acetaminophen and galactose. The current of H₂O₂ reduced by cobalt(II) hexacyanoferrate was found to be proportional to the concentration of glucose in aqueous solutions. The immobilized C60‐GOD enzyme‐based glucose sensor exhibited a good linear response up to 8 mM glucose with a sensitivity of 5.60 × 10² nA/mM and a quite short response time of 5 sec. The C60‐GOD‐based glucose sensor also showed a good sensitivity with a detection limit of 1.6 × 10^‐6 M and a high reproducibility with a relative standard deviation (RSD) of 4.26%. Effects of pH and temperature on the responses of the immobilized C60‐GOD/cobalt(II) hexacyanoferrate‐based electrochemical glucose sensor were also studied and discussed.     

Detection of Hydrogen Peroxide and Glucose Based on Immobilized C60‐Catalase Enzyme

The interaction between fullerene C60 and catalase enzyme was studied with a fullerene C60‐coated piezoelectric (PZ) quartz crystal sensor. The partially irreversible response of the C60‐coated PZ crystal sensor for catalase was observed by the desorption study, which implied that C60 could chemically react with catalase. Thus, immobilized fullerene C60‐catalase enzyme was synthesized and applied in determining hydrogen peroxide in aqueous solutions. An oxygen electrode detector with the immobilized C60‐catalase was also employed to detect oxygen, a product of the hydrolysis of hydrogen peroxide which was catalyzed by the C60‐catalase. The oxygen electrode/C60‐catalase detection system exhibited linear responses to the concentration of hydrogen peroxide and amount of immobilized C60‐catalase enzyme that was used. The effects of pH and temperature on the activity of the immobilized C60‐catalase enzyme were also investigated. Optimum pH at 7.0 and optimum temperature at 25 °C for activity of the insoluble immobilized C60‐catalase enzyme were found. The immobilized C60‐catalase enzyme could be reused with good repeatability of the activity. The lifetime of the immobilized C60‐catalase enzyme was long enough with an activity of 93% after 95 days. The immobilized C60‐catalase enzyme was also applied in determining glucose which was oxidized with glucose oxidase resulting in producing hydrogen peroxide, followed by detecting hydrogen peroxide with the oxygen electrode/C60‐catalase detection system.     

Immobilization of L-glutamate oxidase and peroxidase for glutamate determination in flow injection analysis system

Streptomyces SP.N 14, isolated from soil samples, produced extracellular L-glutamate oxidase (GOD) in liquid culture. After a two-step ammonium sulfate purification and dextran G-150 chromatography, the specific activity was reached at 28.2 U/mg. The partial purified enzyme and horseradish peroxidase (HRP) were covalently coupled to alkylamine controlled pore glass (CPG) by means of glutaraldehyde. About 200–300 U/g of immobilized GOD and 300–400 U/g of immobilized HRP were obtained. The immobilized enzymes were packed into a teflon tube and used in flow injection analysis (FIA) for glutamate in broth. A good linear range was observed for this immobilized enzyme system at 0.1–2.0 mM, and the precision was 2.8% (n = 25). More than 80 samples were measured within an hour. One enzyme column with about 4 U of immobilized GOD and 5 U of immobilized HRP, applied for 50 assays/d, has been used for more than 50 d. The concentration of L-glutamate remaining lower than 2.0 mM, the determination of glutamate in this system was not affected by pH and temperature within the range of 6.0–7.0 and 25–35‡C, respectively. The system was applied to determine L-glutamate in broth samples during L-glutamate fermentation, and good correlation was achieved between results obtained with the system and with the Warburg’s method.     

超细银－金复合颗粒增强酶生物传感器的研究

用琥珀酸二异辛酯磺酸钠／环已烷反胶束体系合成憎水纳米银－金复合颗粒， 并用此纳米银－金颗粒与聚乙烯醇缩丁醛构成复合固酶模基质，用溶胶－凝胶法固 定葡萄糖氧化酶，构建葡萄糖生物传感器。实验表明，纳米憎水银－金颗粒可以大 幅度提高固定化酶的催化活性，响应电流从相应浓度的几十纳安增强几万纳安。探 讨了纳米颗粒效应在固定化酶中所起的作用，为纳米颗粒在生物传感器领域中的应 用提供了可参考的实验和理论依据。     

A Split-Flow Enzyme Thermistor

Abstract

The split-flow system is comprised of two identical micro-columns, one of which contains an immobilized enzyme preparation, the other an inert support material.

The heat produced in each column on introduction of a sample is measured with thermistors placed in these columns. The use of a reference column virtually eliminates the influence on the measurements of artifactual signals as unspecific heat, i.e., heat not produced by the enzymic reaction. The performance of the split-flow enzyme thermistor at a variety of pH's, ionic strengths or viscosities associated with the sample has been investigated and compared with previously described alternative enzyme thermistor arrangements. In this comparative study glucose at a concentration of 5 · 10^?4 M was used throughout. On passage through the imnobilized glucose oxidase preparation this solution gave rise to a heat change At of about 0.01°C. The insensitivity of the system described herein towards such variations makes it particularly suitable for the analysis of metabolities present in crude solutions such as urine and skim-milk.     

Comparative studies on soluble and immobilized rabbit muscle pyruvate kinase

Rabbit muscle pyruvate kinase was immobilized by covalent attachment to a polyacrylamide support (Akrilex C) containing carboxylic functional groups. As a result of immobilization, the pH optimum for catalytic activity shifted into a more alkaline direction. The apparentK _m value with phosphoenolpyruvate increased, and that with ADP slightly decreased. With respect to the stability against urea and thermal inactivation, the immobilized pyruvate kinase seemed to be the more stable at lower urea concentrations and between 45 and 55°C. At 1.5 and 2.5M urea and at higher temperature, there were no marked differences between the soluble and the immobilized enzyme.     

Direct Electron Transfer of Glucose Oxidase and Glucose Biosensor Based on Nano-structural Attapulgite Clay Matrix

The direct electrochemistry of glucose oxidase (GOD) was achieved based on the immobilization of GOD on a natural nano‐structural attapulgite (ATP) clay film modified glassy carbon (GC) electrode. The immobilized GOD displayed a pair of well‐defined quasi‐reversible redox peaks with a formal potential (E^0′) of ?457.5 mV (vs. SCE) in 0.1 mol·L^?1 pH 7.0 phosphate buffer solution. The peak current was linearly dependent on the scan rate, indicating that the direct electrochemistry of GOD in that case was a surface‐controlled process. The immobilized glucose oxidase could retain bioactivity and catalyze the oxidation of glucose in the presence of ferrocene monocarboxylic acid (FMCA) as a mediator with the apparent Michaelis‐Menten constant K^app_m of 1.16 mmol·L^?1. The electrocatalytic response showed a linear dependence on the glucose concentration ranging widely from 5.0×10^?6 to 6.0×10^?4 mol·L^?1 (with correlation coefficient of 0.9960). This work demonstrated that the nano‐structural attapulgite clay was a good candidate material for the direct electrochemistry of the redox‐active enzyme and the construction of the related enzyme biosensors. The proposed biosensors were applied to determine the glucose in blood and urine samples with satisfactory results.     

Stabilization of fumarase activity ofBrevibacterium flavum cells by immobilization with k-carrageenan

Whole cells ofBrevibacterium flavum having fumarase activity were immobilized using K-carrageenan. The stabilities of fumarase activity in the immobilized cells against external factors, including heat, pH, organic solvents, and protein denaturing reagents, were compared with those of free cells and native enzyme. The stabilities of fumarase activity in immobillized cells against external factors were highest, and those of native enzyme were lowest. In the “gel-state,” K-carrageenan-immobilized cells showed a much higher stabilization effect for external factors than “sol-state” immobilized cells.