Application to Whole Cells

Figure 6.4 Directed evolution of KDPGal aldolase for application to whole-cell production of 3-dehydroshikimate...

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. 

P. Reschiglian, A. Zattoni, B. Roda, S. Casolari, M. H. Moon, J. Lee, J. Jung, K. Rodmalm and G. Cenacchi, Bacteria sorting by field-flow fractionation. Application to whole-cell Escherichia coli vaccine strains, Analytical Chemistry, 74, 4895-4904 (2002). 

Compared with isolated enzymes, application of whole cells as biocatalysts is usually more economical since there is no protein purification process involved. Whole cells can be used directly in chemical processes, thereby greatly minimizing formulation costs. Whole cells are cheap to produce and no prior knowledge of genetic details is required. Microorganisms have adapted to the natural environment and produce both simple and complex metabolic products from their nutrient sources through complex, integrated pathways. 

The application of whole-cells or enzyme-based catalysts was protected in two different bioprocess patents ([56] and [57], respectively). The patent specifies the process [57] involving a sulfur-specific reactant with membrane fragments, an enzyme, or a composition of enzymes having the ability to selectively react with sulfur by cleavage of organic C—S bonds, derived from R. rhodochrous strain ATCC No. 53968 or B. sphaericus strain ATCC No. 53969. 

Enzymatic hydroxylation activation has perhaps the highest potential of all enzyme-catalyzed transformations for synthetic applications. Currently, whole-cell processes are used and the outcomes are often unpredictable. The discovery of new oxygenases and efficient hosts for protein expression remain keys to further expanding the synthetic applications of biocatalytic C—H activation [89, 90]. 

The application of whole cells and isolated enzymes in the chemical industry is advancing rapidly, andmany companies areinvesting in so-called white biotechnology. That said, most of the biocatalytic processes are aimed at new compounds which are difficult to synthesize by conventional chemical routes. Replacing an existing chemical process with a biocatalytic route is trickier, because the new process must deliver the same quality of product (or better), at a lower overall cost. The existing process has an advantage here, since its capital costs are already repaid. Thus, in order... 

Brindle, KM., Brown, F.F., Campbell, I.D., Gratwohl, C., Kuchel, P.W. (1979). Application of spin-echo nuclear magnetic resonance to whole cell systems. Biochem. J. 180,37-44. 

Whole plants and animals Applicable to microbes, cells, whole organisms... 

Many transferases are involved in the biosynthesis of compounds of interest to the food, fine chemicals, and pharmaceutical industries. To date, however, there are no commercial processes involving the deliberate use of transferases. The often expensive cofactor requirement hampers their practical applications, although whole cell conversions might offer a solution to this problem. 

Whole-cell based biocatalysis utilizes an entire microorganism for the production of the desired product. One of the oldest examples for industrial applications of whole-cell biocatalysis is the production of acetic acid from ethanol with an immobilized Acetobacter strain, which was developed nearly 200 yr ago. The key advantage of whole-cell biocatalysis is the ability to use cheap and abundant raw materials and catalyze multistep reactions. Recent advances in metabolic engineering have brought a renaissance to whole-cell biocatalysis. In the following sections, two novel industrial processes that utilize whole-cell biocatalysis are discussed with emphasis on the important role played by metabolic engineering. 

In practice, applications requiring whole-cell calculations are rare in the Earth sciences however, it is essential to understand both half-cell and whole-cell sign conventions in designing sample and reference electrode combinations for laboratory or field measurements. This is also necessary to understand how pH, Eh, and specific ion electrodes really function. 

The ionic network formation procedure was originally developed by Thiele and coworkers (11,12) and our laboratory was the first to adopt and modify thisTecFnique to be applicable for whole cell immobilization ( h It was our impression that the contact of the cells with polyelectrolytes and some small electrolytes in aqueous solution only would be most advantageous to maintain high fraction of enzymatic activity and living cells after immobilization. 

The volatility of. SCCO2 makes it easy to isolate analyte SCCO2 is toxic to whole cells in biological applications (CO2 is not toxic to the environment) SCH2O oxidation of toxic, intractable organic waste during water treatment... 

ISPR in biotechnology is applied to whole cell and enzymatic biocatalysis. However, the application of ISPR techniques in enzymatic biocatalysis is not discussed in this publication. This review focuses on ISPR applied to whole cells and gives a complete summary of all work published either in literature or patents within last twenty years. It also includes the key articles that were published before 1980. The following points explain the criteria and restrictions that have been used for the selection of the listed ISPR projects. 

Hai, F I., Yamamoto, K., Nakajima, F. and Fukushi, K. 2011. Application of a GAC-coated hollow fiber module to couple enzymatic degradation of dye on membrane to whole cell biodegradation within a membrane bioreactor./oitrna/ of Membrane Science, 389,67-75. 

Industrial applications of P450s have so far been restricted to whole-cell systems, which mostly solve the problem of cofactor delivery and regeneration. In such instances, however, physiological effects such as limited substrate uptake and reduced efflux of products out of cells, substrate or product toxicity, product degradation, as well as elaborate downstream processing are additional limiting factors that must be taken into account and often require optimization [34]. 

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