Bienzymatic systems

Conversion yields in the bienzymatic system have been optimized by using pure substrates (triglycerides) as well as crude vegetable oils (Table 4) rich in a range of polyunsaturated fatty acids (sunflower oil or linseed oil). The use of crude reactants approaches a more realistic scenario for the industrial-scale manufacture of hydropexides. 

Pezzotti, F. and Therisod, M. (2007) Enantioselective oxidation of thioanisole with an alcohol oxidase/ peroxidase bienzymatic system. Tetrahedron Asymmetry, 18 (6), 701-704. 

O ring. At 20 min inhibition time the detection limits for malathion, parathion methyl and paraoxon were 3, 0.5 and 5pg I respectively. Although these bienzymatic systems look simple, it is difficult to provide optimal conditions for both enzymes. In general the optimum pH, temperature and buffer molarity for different enzymes are different. The experimental conditions are at the levels below the optimum capacity of both enzymes [14], This disadvantage can be minimized by use of a single enzyme system, which is readily inhibited by the pesticide. 

A.A. Ciucu, C. Negulescu, and R.P. Baldwin, Detection of pesticides using an amperometric biosensor based on ferophthalocyanine chemically modified carbon paste electrode and immobilized bienzymatic system. Biosens. Bioelectron. 18, 303-310 (2003). 

An alternative method for coupling enzymes is to employ a mixed enzyme bioreactor Pezzotti and Therisod [60] reported a bienzymatic system in which alcohol oxidase and peroxidase were coupled to effect the enantioselective oxidation of the sulfide thioanisole (Scheme 3.4). Here, the peroxidase from Coprinus dnereus was mixed with a crude extract of Pichia pastoriz alcohol oxidase and the two enzyme mixture was successfully used to convert gram quantities of thioanisole enantiose-lectively to S-methyl-phenyl-sulfoxide with an enantiomeric excess of 75%. 

A bienzymatic system was developed as catalyst for the oxidative polymerization of phenols.18 The HRP-catalyzed polymerization of phenol in the presence of glucose oxidase and glucose gave the polymer in a moderate yield, in which hydrogen peroxide was formed in situ by the oxidative reaction of glucose catalyzed by glucose oxidase. 

ALP + bienzymatic system (NADH oxidase alcohol dehydrogenase (ADH)) NADP+ NAD+ Membrane-covered Pt electrode, 0.60 V vs. Ag/AgCl E 50 amole, T > 20 min 24... 

The combination of the electrochemical detection principle and the recycling of the analyte can be performed as is illustrated in Fig. 5, the bienzymatic system possessing the potential of the highest amplification rate [14]. 

Finally, some biological materials, mainly enzymes, have been introduced into carbon composite matrices and the resulting electrodes used as environmental biosensors (in addition to numerous other biosensing applications ). The main examples are based on tyrosinase (or polyphenol oxidase) for the detection of phenolic compounds or thiols, acetylcholinesterase for organophosphate and carbamate pesticides, ° ° organophosphorous hydrolase for pesticides, or bienzymatic systems for amperometric immunosensor for polycyclic aromatic hydrocarbons. ... 

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