Biocatalysis, use

The best results for the asymmetric cyanohydrination reactions are obtained through biocatalysis, using the readily available enzyme oxynitrilase. This provides cyanohydrins from a number of substances with over 98% ee.146... 

Introduction to Biocatalysis using Enzymes and Microorganisms by Roberts, S.M., Turner, N.J., Willetts, A.J. and Turner, M.K. Cambridge University Press, New York, 1995. 

Roberts, S.M. and Wiletts, A.J., Introduction to Biocatalysis Using Enzymes and Microorganisms, 2nd edition. Cambridge University Press, 1995. 

For an introduction to the use of micro-organisms see Roberts SM, Tm ner NJ, Willetts AJ, Turner MK (1996) Introduction to biocatalysis using enzymes and micro-organisms. Chapter 2, Cambridge University Press... 

Fig. 23.1 Microbial routes from natural raw materials to and between natural flavour compounds (solid arrows). Natural raw materials are depicted within the ellipse. Raw material fractions are derived from their natural sources by conventional means, such as extraction and hydrolysis (dotted arrows). De novo indicates flavour compounds which arise from microbial cultures by de novo biosynthesis (e.g. on glucose or other carbon sources) and not by biotransformation of an externally added precursor. It should be noted that there are many more flavour compounds accessible by biocatalysis using free enzymes which are not described in this chapter, especially flavour esters by esterification of natural alcohols (e.g. aliphatic or terpene alcohols) with natural acids by free lipases. For the sake of completeness, the C6 aldehydes are also shown although only the formation of the corresponding alcohols involves microbial cells as catalysts. The list of flavour compounds shown is not intended to be all-embracing but focuses on the examples discussed in this chapter... 

Catalysis is becoming important and, in the future, biocatalysis (using cells, cell debris, enzymes) may be the most efficient way of producing fine chemicals. 

Khmelnitsky et al. (309) reported the synthesis of solution-phase libraries via combinatorial biocatalysis using a number of different substrates. One of these, bicy-clo[2.2.2]oct-5-ene-2,3-frans dimethanol (BOD, 10.102), is shown in Fig. 10.51 together with the biotransformation strategy that was applied. The selected reactions... 

Figure 3.12 Biocatalysis using organic-aqueous tunable solvents (OATS).

Zhao H (2005) Effect of ions and other compatible solutes on enzyme activity, and its implication for biocatalysis using ionic Uquids. J Mol Catd B Enzym 37 16-25... 

Another example of a coupled enzyme reaction demonstrates the versatility of the transaminase system in biocatalysis. Using a racemic d,L-amino acid mixture as the starting material, the enzyme D-amino acid oxidase from Trigonopsis mriabilis will convert the D-amino acid in the mixture selectively into the corresponding 2-keto acid. The L-amino acid of the d,l- pair is neither a substrate nor an inhibitor of d-amino acid oxidase. If a transaminase is present in the same reaction mixture, the 2-keto acid can be transaminated in the presence of L-aspartate to the corresponding L-amino acid. The entire reaction can be driven to completion as described previously by decarboxylation of the oxaloacetate. Thus, in a single pot, racemic d,l-amino acids can be convened directly into optically active L-amino acids (Fig. 12.7-11). 

Zhang Y, Furyk S, Bergbreiter DE, Cremer PS (2005) Specific ion effects on the water solubility of macromolecules PNIPAM and the Hofmeister series. J Am Chem Soc 127 14505-14510 Zhao HJ (2005) Effects of ions and other compatible solutes on enzymatic activity, and its implication for biocatalysis using ionic liquids. Mol Catal B Enzym 37 16-25... 

It is probably less appreciated that thermodynamics is also of great importance in understanding protein function. This was recognized many years ago by the EFB Working Party on Applied Bio catalysis, who in 1992 organized an international symposium on Fundamentals of Biocatalysis in Non-Conven-tional Media to stimulate the development of a clear scientific base for biocatalysis using non-aqueous solvents [32,33]. 

The first example in the Hterature of continuous-flow biocatalysis using SILP catalyst with a SCCO2 stream was published by Lozano et al. [60]. They grafted the ILs over a polymeric monolithic material and then immobiUzed the enzyme Candida antarctica lipase B (CALB) by simple adsorption of an aqueous solution of the enzyme. With this system, they performed the transesterification reaction of vinyl propionate and citroneUol (Figure 18.13). 

An historical introduction to biocatalysis using enzymes and micro-organisms... 

INTRODUCTION TO BIOCATALYSIS USING ENZYMES AND MICRO-ORGANISMS... 

Poppe L, Novak L (1992) Selective Biocatalysis, Verlag Chemie, Weinheim Cabral JMS, Best D, Boross L, Tramper J (eds) (1994) Applied Biocatalysis, Harwood, Chur Roberts SM, Turner NJ, Willetts AJ, Turner MK (1995) Introduction to Biocatalysis Using Enzymes and Micro-organisms, Cambridge University Press, Cambridge Bomscheuer UT, Kazlauskas RJ (2006) Hydrolases for Organic Synthesis, Wiley-VCH, Weinheim Bommarius AS, Riebel B (2004) Biocatalysis, Fundamentals and Applications, Wiley-VCH, Weinheim... 

To overcome the problem of product inhibition—extractive biocatalysis, use of supramolecular systems for forming inclusion complexes with the product, such as cyclodextrins and crown ethers, have been attempted. 

Rosenbaum M et al (2006) Interfacing electrocatalysis and biocatalysis using tungsten carbide a high performance noble-metal-ffee microbial fuel cell. Angew Chean Int Ed 45 6658-6661... 

Stamatis, H., Xenakis, A. 1999. Biocatalysis using microemulsion-based polymer gels containing lipase. J. Mol. Catal. B Enzym. 6, 399—406. 

Jenta, T.R.-J., Batts, G., Rees, G.D., Robinson, B.H. 1997. Biocatalysis using gelatine microemulsion-based organogels containing immobilized Chromobacterium viscosum lipase. Biotech. Bioeng. 53, 121-131. 

Biocatalysis (using Saccharomyces cereviciae) has been efficiently exploited by Gris et al. [134] for the synthesis of potential, chemotherapic quinoxaline derivatives (Scheme 97) by modification of the specific standard Hinsberg synthetic pathway [135]. The same reaction could also be carried out using MW, which reduces the reaction time as well as increases the yield of the product (Scheme 97) although, for more complex reactions, enzymatic catalysis proved to be a better alternative. Some of the quinoxaline drivatives synthesized by this method exhibited good irihibitor activity against some human tumoral cells and the lymphoma related to HlV-1. 

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