Biocatalyst Classifications

A., and Fraaije, M.W. (2010) Monooxygenases as biocatalysts classification, mechanistic aspects and biotechnological applications. J. Biotechnol., 146, 9-24. 

For biotechnological purposes enzymes are used as biocatalysts to accelerate a desired reaction to its end point. As catalysts enzymes can catalyze a reaction in both directions. Unfortunately the name of an enzyme given by the Enzyme Commission for the classification of enzymes, and biochemistiy text books, stresses the function as a catalyst in one direction only Hydrolases, a group of enzymes of considerable importance in... 

The measure of mass is important with respect to calculating mass balance. However, the elemental composition of biomass is normally ill defined. Another reason for determining biomass is the need for a reference when calculating specific rates (q ) q = r /x. An ideal measure for the biocatalysts in a bioreaction system of interest would be their activity, physiological state, morphology or other classification rather than just their mass. Unfortunately, these are even more difficult to quantify objectively and this is obviously why the biomass concentration is still of the greatest interest. 

Referring to a mechanistic classification of organocatalysts (Seayad and List 2005), currently the two most prominent classes are Brpnsted acid catalysts and Lewis base catalysts. Within the latter class chiral secondary amines (enamine, iminium, dienamine activation for a short review please refer to List 2006) play an important role and can be considered as—by now—already widely extended mimetics of type I aldolases, whereas acylation catalysts, for example, refer to hydrolases or peptidases (Spivey and McDaid 2007). Thiamine-dependent enzymes, a versatile class of C-C bond forming and destructing biocatalysts (Pohl et al. 2002) with their common catalytically active coenzyme thiamine (vitamin Bi), are understood to be the biomimetic roots ofcar-bene catalysis, a further class of nucleophilic, Lewis base catalysis with increasing importance in the last 5 years. 

These enzyme libraries represent the beginning of a new set of biocatalyst tools for the synthetic chemist and were the first thermostable enzyme libraries developed specifically for synthetic chemistry applications in each of these chemical classifications. We have since been expanding the esterase and dehydrogenase libraries using a variety of new and diverse substrate compounds. As... 

Membrane reactors were classically grouped according to the hydrodynam-ics/configuration of the system in CSTR and PFR types [106]. However, this proved vmable to comprise some commonly used types in UF, such as flat membranes or dead-end operated modules and multiphase bioreactors. A classification based on the contact mechanisms that bring together substrate and biocatalyst was thus proposed [110]. Thus, membrane reactors could be divided into direct contact, diffusion contact, and interfacial contact reactors. 

Importance of Biocatalysts Over Chemical Catalysts 455 24.11.1 Classification 24.11.2 Classification 2 24.11.3 LignocellubsiC Degrading 460 461... 

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