Biocatalytic organic reaction

Biocatalytic ledox reactions offer great synthetic utility to organic chemists. The majority of oxidase-catalyzed preparative bioconversions are still performed using a whole-ceU technique, despite the fact that the presence of more than one oxidoreductase in cells often leads to product degradation and lower selectivity. Fortunately, several efficient cofactor regeneration systems have been developed (160), making some cell-free enzymatic bioconversions economically feasible (161,162). 

The same factors discussed in the previous section as being important for biocatalytic reactions in general apply to biocatalytic oxidation reactions as well. In addition, however, another aspect of biocatalysts becomes important the use of cofactors or coenzymes. Many enzymes function with the help of a specific cofactor, a small non-protein organic or metallo-organic group that is capable of facilitating the reaction to be performed. Enzymes that catalyze oxidation re-... 

Interfacial reactions on surfaces are becoming increasingly important due to their widespread applications. Self assembled monolayers (SAMs) provide excellent platforms to study these reactions. This review focuses on the various organic reactions carried out on these SAMs. Challenges and limitations of organic reactions at surfaces are discussed. Emerging biocatalytic techniques for carrying out surface reactions are reviewed. 

An important number of organic reactions are now catalyzed by whole cells or isolated enzymes. However, there are still problems associated with the solubility, yield and selectivity of these biotransformations. Ever since the solubilization of alkaline phosphatase in a mixture of [Et3NH][N03] and water (4 1), it has been known that enzymes can be stable in ionic liquids. Recent research shows that ionic liquids can be used efficiently as a medium for biocatalytic processes. ... 

Hollmann, E., Arends, I.W.C.E., and Buehler, K. (2010) Biocatalytic redox reactions for organic synthesis nonconventional regeneration methods. ChemCatChem, 2 (7),... 

Biocatalytic reduction has been performed in nonaqueous solvents to improve the efficiency of the reaction. This section explains the use of organic solvent, supercritical fluids, and ionic liquid. 

An important problem in emulsified organic-aqueous systems is that of scale-up, which is concerned with the realization of stable emulsions and the separation of phases after the reaction. The use of biphasic membrane systems that contain the enzyme and keep the two phases separated is likely to solve this problem. In the case of 5-naproxen an ee of 92% has been demonstrated without any decay in activity over a period of two weeks of continuous operation. A number of examples of biocatalytic membrane reactors have been provided by Giorno and Drioli (2000) and include the conversion of fumaric acid to L-aspartic acid, L-aspartic acid to L-alanine, and cortexolone to hydrocortisone and prednisolone. 

Since the beginning of the 20th century, organic solvents have been used in enzymatic reaction media [30]. Biocatalytic reactions in water-organic biphasic media were first carried out by Cremonesi et al. [31] and by Buckland et al. [32] less than 30 years ago. Their work aimed at the conversion of high concentrations of poorly water soluble components, particularly steroids. Later, biphasic systems were used for enzyme-catalyzed synthesis reactions that were unfavored in water, changing the reaction equilibrium towards the higher yield of the product, such as esters or peptides. 

The majority of biocatalytic reactions are thermodynamically controlled. Product yield is thus dependent on the equilibrium position of a reaction. Optimization of the product yield requires knowledge of the equilibrium position in different organic solvents. Several works described and compared models for the prediction of the equilibrium position in two-phase media [6, 28, 29, 33]. 

Many interesting biocatalytic reactions involve organic components that are poorly water-soluble. When using organic-aqueous biphasic bioreactor, availability of poorly water-soluble reactants to cells and enzymes is improved, and product extraction can be coupled to the bioreaction. Many applications in two-phase media can use the existing standard-type bioreactors, such as stirred-tank, fluidized-bed, and column reactors with minor adjustments. 

Schilling, M., F. Patett et al. (2007). Influence of solubility-enhancing fusion proteins and organic solvents on the in vitro biocatalytic performance of the carotenoid cleavage dioxygenase AtCCDl in a micellar reaction system. Appl. Microbiol. Biotechnol. 75(4) 829-836. 

The above mixture is incubated. The water-soluble salt contaminants would transfer from the fossil fuel into the aqueous phase during the procedure. Secondly, the biocatalytic agent would selectively break C—S bonds in the sulfur-bearing molecules to form water-soluble inorganic sulfur molecules. Both of these reactions occur without depleting the fossil fuel of combustible organic molecules and... 

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