Biocatalysis microorganism enzyme

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. 

Today, biocatalysis represents a well-established field of research at crossroads between chemistry, biology, chemical engineering, and bioengineering, and dealing with the application of biological systems such as microorganisms, enzymes, or... 

Recently, recombinant biocatalysts obtained using Escherichia coli cells were designed for this process. The overexpression of all enzymes required for the process, namely, hydantoinase, carbamoylase, and hydantoin racemase from Arthrobacter sp. DSM 9771 was achieved. These cells were used for production of a-amino acids at the concentration of above 50 g 1 dry cell weight [37]. This is an excellent example presenting the power of biocatalysis with respect to classical catalysis, since a simultaneous use of three different biocatalysts originated from one microorganism can be easily achieved. 

Some of the industrial biocatalysts are nitrile hydralase (Nitto Chemicals), which has a productivity of 50 g acrylamide per litre per hour penicillin G amidase (Smith Kline Beechem and others), which has a productivity of 1 - 2 tonnes 6-APA per kg of the immobilized enzyme glucose isomerase (Novo Nordisk, etc.), which has a productivity of 20 tonnes of high fmctose syrup per kg of immobilized enzyme (Cheetham, 1998). Wandrey et al. (2000) have given an account of industrial biocatalysis past, present, and future. It appears that more than 100 different biotransformations are carried out in industry. In the case of isolated enzymes the cost of enzyme is expected to drop due to an efficient production with genetically engineered microorganisms or higher cells. Rozzell (1999) has discussed myths and realities... 

Much of industrial chemistry takes place in organic solvents, or involves apolar compounds. Biocatalysis, in contrast, typically involves aqueous environments. Nevertheless, enzymes and microorganisms do in fact encounter apolar environments in Nature. Every cell is surrounded by at least one cell membrane, and more complex eukaryotic cells contain large amounts of intracellular membrane systems. These membranes consist of lipid bilayers into which many proteins are inserted present estimates, based on genomic information, are that about one-third of all proteins are membrane proteins, many of which are so-called intrinsic proteins that are intimately threaded through the apolar bilayer. These proteins are essentially dissolved in, and function partly within, an apolar phase. 

Microbial reduction has been recognized for decades as a laboratory method of preparing alcohols from ketones with exquisite enantioselectivity. The baker s yeast system represents one of the better known examples of biocatalysis, taught on many undergraduate chemistry courses. Numerous other microorganisms also produce the ADH enzymes (KREDs) responsible for asymmetric ketone reduction, and so suitable biocatalysts have traditionally been identified by extensive microbial screening. Homann et have... 

An ionic liquid can be used as a pure solvent or as a co-solvent. An enzyme-ionic liquid system can be operated in a single phase or in multiple phases. Although most research has focused on enzymatic catalysis in ionic liquids, application to whole cell systems has also been reported (272). Besides searches for an alternative non-volatile and polar media with reduced water and orgamc solvents for biocatalysis, significant attention has been paid to the dispersion of enzymes and microorganisms in ionic liquids so that repeated use of the expensive biocatalysts can be realized. Another incentive for biocatalysis in ionic liquid media is to take advantage of the tunability of the solvent properties of the ionic liquids to achieve improved catalytic performance. Because biocatalysts are applied predominantly at lower temperatures (occasionally exceeding 100°C), thermal stability limitations of ionic liquids are typically not a concern. Instead, the solvent properties are most critical to the performance of biocatalysts. 

Molecular cloning is now a standard procedure to overproduce specific enzymes of use in biocatalysis in a host microorganism that is suited for the process. The host strain should fulfil the objectives of downstream processing, which are high recovery, high purity, reproducibility and low cost scale-up. 

A high profile example of biocatalysis patenting is that of Taq polymerase, the thermostable DNA polymerase enzyme isolated from the thermophilic microorganism... 

Most studies of biocatalysis in ionic liquids have been concerned with the use of isolated enzymes. It should not be overlooked, however, that the first report on biocatalysis and ionic liquids involved a whole-cell preparation Rhodococcus R312 in a biphasic [BMIm][PF(s]-water system [7]. It was shown, using a nitrile hydrolysis test reaction, that the microorganism maintained its activity better in ionic liquid than in a biphasic toluene-water system. 

A wider available panel of purified enzymes, or of characterized microorganisms performing a particular biotransformation, could increase the potential of this technique. Its main limitations are the stability of the enzymes, both to organic solvents and to different temperatures, which could be significantly improved by their immobilization on a solid support, and the solubility in aqueous media required in most cases for the biotransformation substrates. Anyway, the extreme usefulness of combinatorial biocatalysis for specific classes of products (complex natural products, polyfunctionalized chiral scaffolds) has already been assessed. 

CCCs may obtain chiral compounds by classical resolution, kinetic resolution using chemical or enzymatic metlrods, biocatalysis (enzyme systems, whole cells, or cell isolates), fermentation (from growing whole microorganisms), and stereoselective chemistry (e.g., asymmetric reduction, low-temperature reactions, use of chiral auxiliaries). CCCs may also be CCEs by capitalizing on a key raw material position and going downstream. Along with companies manufacturing chiral molecules primarily for other purposes, such as amino acid producers, these will be the key sources for the asymmetric center. 

Biocatalysis includes both enzyme catalysis and biotransformation using whole microorganisms. 

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