Microbial enzymes, tailoring

Tailoring Opportunities. There are many methods or approaches available to tailor enzyme products. Early in the history of enzyme companies, methods such as source selection, microbial strain selection, growth conditions, media, purification, and recovery systems, were primarily used to make each enzyme preparation unique. Later, immobilization, encapsulation, and chemical modification of the enzyme molecule itself were added as methods of tailoring enzymes to better fit industrial applications. Today, all of these methods are still being used, and now we have added genetic engineering to our tailoring expertises. 

Enzyme-based applications for environmental screening or monitoring demand tailored biocatalysts performing catalysis in non-natural substrates and/or in non-usual or hostile media. Moreover, the increased complexity of contaminated environmental sites also demands efiicient biodegradation of xenobiotic compounds through new and multiple engineered pathways where the tailored biocatalysts should perform in their host microbial cells [434]. 

The generation of individual flavor compounds or complex flavor mixrnres by the use of microorganisms and enzymes, the topic of subsequent symposium contributions, is summarized. The two basic approaches, de novo-synthesis in the course of microbial fermentations and biotransformations of suitable precursors are outlined. The increased compositional and strucmral knowledge of the substrates/precursors needed and the tailor-made design of the microorganisms/enzymes employed are presented as bases for strategies to optimize the biogeneration of flavors. 

Various shapes of immobilized enzymes and microbial cells suitable for their application purposes can be easily tailored. 

The main distinction between them is that in an enzymatic reaction, the enzyme, a lifeless chemical entity, does not reproduce. On the other hand, in microbial transformation, the reaction occurs within a living cell where it is catalyzed by the enzyme produced by it (just as in an enzymatic reaction). However, the cell also reproduces itself, generating more enzyme in the process. Thus the modeling of microbial reactions must take this growth process into account. Further, these reactions can produce three possible results, as shown in Table 20.3. The reaction can be tailored specifically to produce any one of these results. Our concern in this chapter is with result 1, the production of a specific product R. 

---