Biocatalysis Bioconversion

Previously, we have shown that functional secretion of OPH molecules into the periplasmic space induced about 2.8-fold higher specific whole cell OPH activity [10]. From the detail reaction kinetic studies in this work, we showed that this periplasmic space-secretion strategy provided much improved bioconversion capability and efficiency ( 1.8-fold) for Paraoxon as a model organophosphate compound. From these results, we confirmed that Tat-driven periplasmic secretion of OPH can be successfully employed to develop a whole cell biocatalysis system with notable enhanced bioconversion efficiency and capability for environmental toxic organophosphates. 

The protein-containing colloidal solutions of water-in-organic solvents are optically transparent. Hence, absorption spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy are found to be convenient for studying biocatalysis [53]. The reversed micelles are interesting models for studying bioconversion, since the majority of the enzymes in vivo act inside or on the surface of biological membranes. 

Bergeron S, Chaplin D, Edwards JH, Ellis BS, Hill CL, Holt-Tiffin K, Knight JR, Mahoney T, Osborne AP, Ruecroft G (2006) Nitrilase-catalyzed desym-metrization of 3-hydroxyglutaronitrile preparation of a statin side-chain intermediate. Org Proc Res Dev 10 661-665 Burns M, Weaver J, Wong J (2005) Stereoselective enzymic bioconversion of aliphatic dinitriles into cyano carboxylic acids. WO 2005100580 DeSantis G, Zhu Z, Greenberg W, Wong K, Chaplin J, Hanson SR, Farwell B, Nicholson LW, Rand CL, Weiner DP, Robertson D, Burk MJ (2002) An enzyme library approach to biocatalysis development of nitrilases for enantioselective production of carboxylic acid derivatives. J Am Chem Soc 124 9024-9025... 

Biocatalysis. Biocatalysis, also termed biotransformation and bioconversion, makes use of natural or modified isolated enzymes, enzyme extracts, or whole-cell systems for the production of small molecules. A starting material is converted by the biocatalyst in the desired product. Enzymes are differentiated from chemical catalysts particularly with regard to stereoselectivity. 

The applications of biocatalysis that are treated in this chapter are bioconversions that fulfil a number of criteria. These are that they ... 

Biocatalysis is one of a number of forms of chemical catalysis (Fig. 1) that can be utilized to synthesize a variety of organic chemicals. Over 60% of the 135 MM tons of organic chemicals produced in the United States involve a catalytic step somewhere in their manufacture (1,2). In recent years many reports and reviews extolling the virtues of biocatalysis for the production of chemicals have been released (e.g., 3-9). However, there have still been very few examples of commercial chemical processes introduced in the last few years that utilize a biocatalyst, for example, the acrylamide process (10-12). There has been small but growing concern as to the validity of the expectations placed on bioconversion-based chemical process (13). 

The power of directed evolution is now well documented. These methods are robust and are able to improve industrial enzymes in reasonably short times. The first laboratory-evolved enzymes are now used commercially in laundry detergents12011 other commercial applications are on the horizon. Directed evolution may well help move biocatalysis from an enabling tool to a lowest cost approach . It also offers new opportunities to engineer multi-enzyme pathways and even whole microbes [69- 224> 2251, which will lead to straightforward single-pot, multi-enzyme bioconversions and new fermentation processes based on green resources such as glucose or inexpensive waste materials. 

The basic principles of bioconversion, bioreactors and biocatalysis are introduced, together with a description of the most important biocatalyst immobilization techniques. The mass transfer phenomena involved in membrane systems are discussed along with some representative configurations of membrane bioreactors, whose behaviour can be described using a simple mathematical approach. For all the aforementioned systems the most significant parameters have been defined to estimate the system performance. 

In Part I a selection of the types of membrane reactor is presented, together with chapters on the integration of membrane reactors with current industrial processes. To summarize, in Chapter 1 (Calabro) membrane bioreactors are described from an engineering point of view, together with a straightforward description and simulation, with a simple mathematical approach, of the most important configurations and processes in which they are involved. Basic principles of bioconversion, bioreactors and biocatalysis with immobilized biocatalysts are also presented. For all the cited systems the most significant parameters are defined in order to estimate their performances. The best approaches for the preparation of... 

Nagasawa T, Yamada H (1990) Large-scale bioconversion of nitriles into useful amides and acids. In Abramowicz DA (ed) Biocatalysis.Van Nostrand Reinhold, New York, p 277... 

Biocatalysis in organic solvents has unique advantages compared to traditional aqueous enzymology/fermentation. Often times in nonaqueous media enzymes exhibit properties drastically different from those displayed in aqueous buffers. These novel properties are given in Table 4.3. In addition to those mentioned in Table 4.3, the solubility of hydrophobic substrates and/or products increases in organic solvents, which diminishes diffusional barriers for bioconversions, and thus speeds up the reactions and improves the potential for direct applications in industrial chemical processes. Once organic solvent becomes a reaction medium, there cannot be contamination, which thus precludes release of proteolytic enzymes by microbes and favors the direct application of the process in an industrial setting. Most proteins (enzymes) inherently function in an aqueous environment, and hence their behavior in nonaqueous solvents is completely different due to the loss in the three-dimensional structure. Thus, only polar solvents... 

Future applications of biocatalysis will be related to discovery of novel activities and substrate relationships (21). As mentioned earlier in this paper, high throughput NMR spectroscopy provides a mechanism to discover such new enzymatic activities and chemistry. To date, this technology has been applied to substrate bioconversions. However, the application can be extended to the discovery of biocatalysis applications to polymer science. 

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