Enzymatic reactions compared with chemical methods

Biodiesel (long-chain monoalkyl fatty acid esters), a renewable and green fuel, is made from vegetable oil or animal fats. At present, the high cost of biodiesel, of which the raw material amounts to 75%, prohibits its wide application. Compared with chemical method, enzymatic process seems to be a promising alternative because of its mild reaction conditions, easy recovery of product, being free of chemical wastes and low demangding on raw materials, which makes it possible to use waste oil as substrate for enzymatic production of biodiesel. 

Goto et al. demonstrated the integration of a bioassay system that illustrated all processes required for a bioassay, that is, cell culture, chemical stimulation of cells, chemical and enzymatic reactions, and detection, on a chip using CFCP (Figure 35.10). By using the temperature control device, spatial temperature control of the system was possible, with areas on the chip maintained at different temperatures. Nitric oxide released from macrophage-like cells stimulated by lipopolysac-charide was successfully monitored by this system. The total assay time was reduced from 24 to 4 h, and the detection limit for nitric oxide was improved from 1 x 10 m to 7 x 10 M compared with the conventional batch methods. Moreover, the system could monitor a time course of the release, which is difficult to measure by conventional methods. 

Two examples of enzymatic systems that mediate bond-formation reactions are the aminotransferases (Equation 17) [98] and the lyases (Equation 18) [99] these show great promise for development of the field. Generally, enzymatic synthesis can offer significant advantages, such as ease of execution and the isolation of products with high optical purity. Indeed, any chemical method that is intended for use on process scale must compare favorably with the high standard set by enzymatic methods. 

The unique advantage of the Laue method is that data can be collected rapidly enough to give a freeze-frame picture of the crystal s contents. Typical X-ray data are averaged over the time of data collection, which can be hours, days, or even months, and over the sometimes large number of crystals required to obtain a complete data set. Laue data has been collected with X-ray pulses shorter than 200 picoseconds. Such short time periods for data collection are comparable to half-times for chemical reactions, especially those involving macromolecules, such as enzymatic catalysis. This raises the possibility of determining the structures of reaction intermediates. 

The FDP-aldolase catalyzed DHAP-addition to glyoxylic acid, examined in detail by Wandrey and Bossow-Berke under continuous flow reaction conditions [18], required the determination of the relative and absolute configuration. Employing the SAMP-/RAMP-hydrazone method, the aldol reaction of 1 with benzyl glyoxylate afforded a doubly protected adduct, which was deprotected with trifluoroacetic acid anhydride (TFAA) and subsequent debenzylation with H2/ Pd-C to give the final product, identical with the enzyme product. The independent chemical synthesis and the enzymatic route are compared in scheme 4. It... 

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