Whole cell technology

Fig. 3.41 Whole cell technology for biocatalytic reduction, example adapted from Ref. [117],...

Much higher productivities can be obtained using isolated enzymes or cell extracts [118]. This approach is therefore highly preferred. Because of the importance of whole cell technology for biocatalytic reduction a few examples will be given. However the main part of this chapter will be devoted to industrial examples of bioreduction involving isolated enzymes and cofactor recycling. 

Whole cells are grown for a variety of reasons. The cells may perform a desired transformation of the substrate, e.g., wastewater treatment the cells themselves may be the desired produce, e.g., yeast production or the cells may produce a desired product, e.g., penicillin. In the later case, the desired product may be excreted, as for the penicillin example, and recovered in relatively simple fashion. If the desired product is retained within the cell walls, it is necessary to lyse (rupture) the cells and recover the product from a complex mixture of cellular proteins. This approach is often needed for therapeutic proteins that are created by recombinant DNA technology. The resulting separation problem is one of the more challenging aspects of biochemical engineering. However, culture of the cells can be quite difficult experimentally and is even more demanding theoretically. 

Gong, P.-F. and Xu, J.-H. (2005) Bio-resolution of a chiral epoxide using whole cells of Bacillus megaterium ECU1001 in a biphasic system. Enzyme and Microbial Technology, 36, 252-257. 

During the last decade, significant advancements in biochemistry, molecular cloning, and random and site-directed mutagenesis, directed evolution of biocatalysts, metabolic engineering and fermentation technology have led us to devise methods to circumvent the disadvantages of whole-cell biotransformation discussed in Section 10.2. The applications of these methods are summarized in this section. 

In order to extend the biocatalytic activities of the biotransformation processes and reduce the frequency of producing cell mass and undesirable side products, immobilized-cell technology has been successfully applied to the whole-cell biotransformation processes. In addition to the three commercial immobilized whole-cell biotransformation processes shown in Table 10.1, examples of immobilization of three different microorganisms for whole-cell biotransformations are shown below to demonstrate the broad application of the immobilized whole-cell biotransformation processes. 

Cruz, A., Fernandes, P., Cabral, J.M.S. and Pinheiro, H.M. (2004) Solvent partitioning and whole-cell sitosterol bioconversion activity in aqueous-organic two-phase systems. Enzyme and Microbial Technology, 34, 342-353. 

Engelking, H., Pfaller, R., Wich, G. and Weuster-Botz, D. (2006) Reaction engineering studies on /3-ketoester reductions with whole cells of recombinant Saccharomyces cerevisiae. Enzyme and Microbial Technology, 38, 536-544. 

Prichanont, S., Leak, D.J. and Stuckey, D.C. (1998) Alkene monooxygenase-catalyzed whole cell epoxidation in a two-liquid phase system. Enzyme and Microbial Technology, 22 (6), 471 479. 

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