Engineering biocatalyst

Improvement of rates is mainly the result of biocatalyst engineering, while improvement of yields result from the biocatalyst selectivity and from mass transport between phases. This last phenomenon is also a key feature for environmental aspects. Hence, most of the impacts of a biological process deal with carbon release in the environment. This release takes place in the form of VOCs, including CO2. If it is difficult to avoid CO2 production when microorganisms are involved (it is still the same with enzymes because they were preliminary produced by cell cultivation), care can be taken for other organic compounds. 

Schneider, S., Wubbolts, M. G., Sanglard, D., and Witholt, B. 1998. Biocatalyst engineering by assembly of fatty acid transport and oxidation activities for in vivo application of cytochrome P-450(BM-3) monooxygenase. Appl. Environ. Microbiol.,... 

The characteristics of limited operating regions, substrate or product inhibition, and reactions in aqueous solutions have often been considered as the most serious drawbacks of biocatalysts. Many of these drawbacks, however, turn out to be misconceptions and prejudices.For example, many commercially used enzymes show excellent stability with half-lives of months or even years under process conditions. In addition, there is an enzyme-catalyzed reaction equivalent to almost every type of known organic reaction. Many enzymes can accept non-natural substrates and convert them into desired products. More importantly, almost all of the biocatalyst characteristics can be tailored with protein engineering and metabolic engineering methods (refer to the section Biocatalyst Engineering and see also the entry Protein Design ) to meet the desired process conditions. 

With directed evolution we can engineer enzyme properties rapidly and with a high probability of success. Many enzymes that have been improved by directed evolution are listed in Tab. 4-3. This powerful biocatalyst engineering strategy creates new opportunities in organic synthesis new and improved bioconversion processes can be developed and novel compounds that are otherwise inaccessible by classical chemistry can be synthesized. In addition, the molecules created by directed evolution offer an excellent opportunity for improving our still poor understanding of sequence-structure-function relationships. 

Tlie factors determining the industrial and economic feasibility of biocatalytic processes are depicted in Figirre 8.2, showing the key aspects of the syntlietic process (and its economics), biocatalyst selection and characterization, biocatalyst engineering, its application in industrial use, and product recovery. 

Biocatalysis in general and in non-conventional media biocatalyst engineering, protein engineering, DSP, inclusion body reprocessing... 

Empirical Biocatalyst Engineering Escaping the Tyranny of High-Throughput Screening... 

In this chapter, we have summarized striking examples of cascade reactions for the chemo-enzymatic synthesis of glycoconjugates. The benefit of cascade reactions without intermediate product work-up is emerging in the field of glycan synthesis. Future studies should be therefore directed toward biocatalyst engineering and process design to match the requirements for sequential, one-pot, and convergent cascade reactions. 

The first two strategies are based on chemical and structural modifications of the starting material (substrate engineering), whereas the last two are related to the nature of active catalytic site of the enzyme (biocatalyst engineering). 

Lorenz, R Eck, J., Screening for novel industrial biocatalysts. Engineering in Life Sciences 2004,4(6), 501-504. 

Due to the complexity of biocatalyst engineering and its limitations when using site-directed mutagenesis of a few mutational sites, in vitro enzyme evolution has emerged as an additional powerful tool for improving enzymes [48]. Using this... 

Most complex is that improvements in both the biocatalyst(s) and the process need to go hand in hand. Consequently process engineers have an important role here in integrating the targets required for a cost-effective process together with the possibilities provided by die "biocatalyst engineers" [69]. 

---