Biocatalysts biocatalytic

The patents, however, protected the microorganisms (biocatalysts/biocatalytic systems) [86,87] as well as process to use the microorganism [87], So far, there are no records of any other international protection. The patent reports new cultures of Rhodococcus strains, and a method to improve biocatalyst stability, which allows recycling. 

It is apparent that the use of enzymatic catalysis continues to grow Greater availabiUty of enzymes, development of new methodologies for thek utilization, investigation of enzymatic behavior in nonconventional environments, and the design and synthesis of new biocatalysts with altered selectivity and increased stabiUty are essential for the successhil development of this field. As more is learned about selectivity of enzymes toward unnatural substrates, the choice of an enzyme for a particular transformation will become easier to predict. It should simplify a search for an appropriate catalyst and help to estabhsh biocatalytic procedures as a usehil supplement to classical organic synthesis. 

In this chapter, we try to summarize the work so far reported in this field. We first give a short introduction into the different forms of biocatalytic reactions, highlighting some special properties of biocatalysts. 

Biotechnology has attracted enormous interest and high expectations over the past decade. However, the implementation of new technologies into industrial processes has been slower than initially predicted. Although biocatalytic methods hold great industrial potential, there are relatively few commercial applications of biocatalysts in organic chemical synthesis. The main factors that limit the application of biocatalysts are ... 

Chiral epoxides and their corresponding vicinal diols are very important intermediates in asymmetric synthesis [163]. Chiral nonracemic epoxides can be obtained through asymmetric epoxidation using either chemical catalysts [164] or enzymes [165-167]. Biocatalytic epoxidations require sophisticated techniques and have thus far found limited application. An alternative approach is the asymmetric hydrolysis of racemic or meso-epoxides using transition-metal catalysts [168] or biocatalysts [169-174]. Epoxide hydrolases (EHs) (EC 3.3.2.3) catalyze the conversion of epoxides to their corresponding vicinal diols. EHs are cofactor-independent enzymes that are almost ubiquitous in nature. They are usually employed as whole cells or crude... 

Since stereoselectivities of biocatalytic reductions are not always satisfactory, modification of biocatalysis are necessary for practical use. This section explains how to find, prepare, and modify the suitable biocatalysts, how to recycle the coenzyme, and how to improve productivity and enantioselectivity of the reactions. 

Biocatalytic Deracemization Dynamic Resolution, Stereoinversion, Enantioconvergent Processes and Cyclic Deracemization, in Biocatalysts in the Pharmaceutical and Biotechnology industries, (ed. R.N. Patel), CRC Press, Boca Raton, pp. 27-51. 

In the present work, for detail kinetic studies, we compared biocatalytic reaction kinetics for four types of whole cell biocatalyst systems whole cells with periplasmic-secreting OPH under trc or T7 promoters and whole cells with cytoplasmic-expressing OPH imder trc or T7 promoters. 

As each BVMO is limited in substrate specificity, it is crucial to have a large collection of these oxidative biocatalysts available. Except for expanding the scope of possible reactions, a large toolbox of BVMOs would also increase the chance of being able to perform any wanted specific chemo-, regio- and/or enantioselective reaction. This contrasts with the present situation as only a relatively small number of BVMOs can be exploited for biocatalytic purposes. Therefore, it is still crucial to discover or engineer BVMOs with novel biocatalytic properties. 

A combinatorial approach for biocatalytic production of polyesters was demonstrated. A library of polyesters were synthesized in 96 deep-well plates from a combination of divinyl esters and glycols with lipases of different origin. In this screening, lipase CA was confirmed to be the most active biocatalyst for the polyester production. As acyl acceptor, 2,2,2-trifluoroethyl esters and vinyl esters were examined and the former produced the polymer of higher molecular weight. Various monomers such as carbohydrates, nucleic acids, and a natural steroid diol were used as acyl acceptor. 

The pectinase was supported on y-alumina and the three enzymes present in the pectinase sample were found still active after the immobilisation. The supported biocatalyst was used in several reaction cycles to perform consecutive depectinisations of a cloudy apple juice with a negligible loss of biocatalytic activity. 

The biocatalytic approach is based on recombinant Escherichia coli growing in an aqueous mineral medium (Scheme 5.4). In Scheme 5.4, microbial growth is translated into a stoichiometric equation for biocatalyst synthesis. One needs to consider that biological safety regulations for recombinant class 1 organisms (no danger for humans and the environment) have to be followed with respect to biocatalyst handling. 

Figure 5.8 Environmental factors E (top figure) and cost indices Cl (bottom figure) for the biocatalytic (a) and chemical catalytic (b) syntheses of (5)-styrene oxide (Scheme 5.3) including the synthesis of the Jacobsen catalyst and of the bacteria (Scheme 5.4) as further syntheses. Waste produced during biocatalyst synthesis is indicated. However, it has to be considered that biocatalyst and product synthesis cannot be separated.

Biocatalytic membrane electrodes have an ISE or a gas sensing electrode in contact with a thin layer of biocatalytic material, which can be an immobilized enzyme, bacterial particles or a tissue slice, as shown in Fig. 3 The biocatalyst converts substrate (the analyte) into product, which is measured by the electrode. Electrodes of this type are often referred to as biosensors . 

Typically, a biocatalytic process for oil refining involves several stages beginning with biocatalyst production. This involves growth of the microorganism via fermentation... 

The application of biocatalytic technologies in the refining industry will be possible only if it can improve product yields and produce cleaner fuels economically. The hurdle to commercialization of the biodesulfurization process is still the activity of the biocatalyst. The reasons for this will be evident from the discussion in Chapter 3. 

The limitations preventing commercialization are mainly related to biocatalyst activity and specificity. Currently, increasing rate with respect to the biocatalyst is the main objective of the biocatalytic refining processes being developed. New applications of by-products could contribute to improving economic parameters. 

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