Invertase and glucose oxidase

As a start on such a series and by modifying the kinetic treatment of Ramachandran while retaining the use of the collocation method, the present authors have successfully analyzed experimental observations made on the system of reaction scheme (2). Both invertase and glucose oxidase were coimmobilized by entrapment in gels of poly(hydroxy ethylmethacrylate) (PHEMA) or of poly(hydroxy ethylmetha-crylate-co-4-vinyl pyridine) (PHEMA-VP). Some of the more significant results are presented below for details and more extensive results, the reader is referred elsewhere (18,19,20). 

INVERTASE AND GLUCOSE OXIDASE COENTRAPPED IN PHEMA Summary of Experimental Work... 

Gursel, A Alkan, S Toppare, L Yagci, Y. ImmobiUzation of Invertase and Glucose Oxidase in Conducting H-lype Polysiloxane/Polypyrrole Block Copolymers. Reactive and Functional Polymers, 2003 57, 57-65. 

Fig. 20.4. Calibration curve for inhibition of invertase (0.05 pg/mL) by methyl mercury after 10-min incubation using biphasic system (phosphate buffer/ toluene mixture) and glucose oxidase biosensor. Eapp — +0.60 V vs. Ag/AgCl and reaction time = 5 min.

Production of citric acid, enzymes (such as amylases, invertase, proteases, glucose oxidase, and pectinase), fumaric acid, gluconic acid, and lactic acid... 

Using the manifold shown in Fig. 4.49, the injected sample of sucrose is first directed to a packed reactor (MGC) containing coimmobilized mu-tarotase, glucose oxidase, and catalase, which decomposes any glucose already present in the sample, and then on to a second reactor (IMG) containing coimmobilized invertase, mutarotase, and glucose oxidase in which the sucrose via the reactions described above is degraded to hy-... 

Microbes have long been used as dependable sources of such industrial enzymes as amylase, invertase, lactase, protease, pectinase, catalase, and glucose oxidase. The interest in fermentation enzymes seems, to be rapidly expanding as demonstrated by the current activity in the following areas ... 

Scheller F, Karsten C. A combination of invertase reactor and glucose oxidase electrode for the successive determination of glucose and sucrose. Anal Chim Acta 1983 155 29-36. 

For the PHEMA-VP gel the existence of a maximum is observed, which is readily understood as the result of a transition from invertase to glucose oxidase being the rate controlling reagent. In PHEMA, however, no maximum is observed and this is because there is so little mutarotation occurring, all outside the gel phase, that it is always the rate controlling step. 

Matsumoto et al (41) prepared a multi-enzyme electrode using glucose oxidase, invertase, mutarotase, fructose-5-dehydrogenase, and catalase to simultaneously detect glucose, fructose, and sucrose in fruit juices and soft drinks. Detection of multi-components by enzyme sensors was also reported in analysis of sucrose and glucose in honey (42) and drinks (43), and L-malate and L-lactate in wines (44). 

Jawaheer et al. [12] Fruits (maturity and quality) Glucose oxidase, mutarotase, invertase/ pectin matrix and covered with a cellulose acetate (CA) membrane Screen-printed rhodinised carbon electrodes/ +350mV vs. Ag/AgCl ... 

The feasibility of amperometric sucrose and mercury biosensors based on the immobilization of invertase, glucose oxidase, and muta-rotase entrapped in a clay matrix (laponite) was investigated by Mohammadi et al. [31]. In this work, the effect of pH of a tri-enzymatic biosensor in which the optimum pH of the three enzymes is different (Invertase, pH 4.5 Glucose oxidase, pH 5.5 and Mutarotase, pH 7.4) [41] was studied. The pH effect on the biosensor response was analyzed between pH 4 and 8 and the highest activity was found at pH 6.0. In order to improve the selectivity of the invertase toward mercury and to avoid silver interference, a medium exchange technique was carried out. The biosensor was exposed to mercury in an acetate buffer solution at pH 4 while the residual activity was evaluated with phosphate buffer solution at pH 6 [41]. 

Fig. 20.1. Dependence of glucose oxidase biosensors and invertase on pH values for 20 mM of sucrose addition and 5 min as reaction time. Experimental conditions Invertase (4pg/mL) acetate buffer ( ) and phosphate buffer ( ) Eapp = + 0.60 V vs. Ag/AgCl.

Fig. 20.3. Calibration plots for methyl mercury obtained in phosphate buffer (curve a) and biphasic system (phosphate buffer/toluene mixture curve b) using the glucose oxidase biosensor and invertase in solution 0.15 pg/mL, I app = + 0.60 V vs. Ag/AgCl reaction time = 5 min and incubation time-10 min.

The principle of combination of electrochemical glucose oxidase biosensor with the clean-up method for direct extraction and determination of methyl mercury has been successfully demonstrated. The extraction of methyl mercury from the organic solvent has been based on invertase enzyme inhibition. The combination of very low concentration of invertase enzyme and 10 min of incubation time allows the detection of methyl mercury at 5 ppb level. Our method permits the detection of this inhibitor below the legal limit given by the European Union with good recoveries when fish samples were measured. 

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