Biochemical catalytic production using

In terms of biodiesel conversion processes, chemical conversion using alkali and acid-based catalysts is stiU the most favorite approach. Various investigations have been carried out to develop novel catalysts and/or novel processes for efficient conversion of TAG to FAME. This part was reviewed in the chapter Production of biodiesel via catalytic upgrading refining of sustainable oleageneous feedstocks. The chapter Biochemical catalytic production of biodiesel introduced a promising alternative way of biodiesel production via enzyme-catalyzed processes. Recentiy, microalgae... 

With the technical development achieved in the last 30 years, pressure has become a common variable in several chemical and biochemical laboratories. In addition to temperature, concentration, pH, solvent, ionic strength, etc., it helps provide a better understanding of structures and reactions in chemical, biochemical, catalytic-mechanistic studies and industrial applications. Two of the first industrial examples of the effect of pressure on reactions are the Haber process for the synthesis of ammonia and the conversion of carbon to diamond. The production of NH3 and synthetic diamonds illustrate completely different fields of use of high pressures the first application concerns reactions involving pressurized gases and the second deals with the effect of very high hydrostatic pressure on chemical reactions. High pressure analytical techniques have been developed for the majority of the physicochemical methods (spectroscopies e. g. NMR, IR, UV-visible and electrochemistry, flow methods, etc.). 

However valuable kinetic studies are, they reveal little about how enzymes catalyze biochemical reactions. Biochemists use other techniques to investigate the catalytic mechanisms of enzymes. (A mechanism is a set of steps in a chemical reaction by which a substrate is changed into a product.) Enzyme mechanism investigations seek to relate enzyme activity to the structure and function of the active site. X-ray crystallography, chemical inactivation of active site side chains, and studies using simple model compounds as substrates and as inhibitors are used. 

With the exception of natural rubber, all the above polymers are synthetic products. Although this book will deal with the properties of synthetic materials only, we have to be aware of the decisive role played by polymers in nature. Control of life processes is based on two polymer species, nucleic acids and proteins. The specific property of these polymers is that they form stable microscopic objects, mainly as the result of the action of intramolecular hydrogen bonds. The stable, specifically ordered surface of the proteins provides the high selectivity and catalytic potential used in biochemical reactions selectivity and catalytic activity disappear when the globular molecular shape is destroyed at elevated temperatures or upon the addition of an active chemical agent. The synthetic polymers discussed in this book do not possess the potential to form a unique molecular conformation as single chains and, therefore, do not show any biochemical activity. 

Autocatalysis. In some reactions, one of the products acts as a catalyst, and the rate of reaction is experimentally observed to increase and go through a maximum as reactant is used up. This is autocatalysis. Some biochemical reactions are autocatalytic. The existence of autocatalysis may appear to contradict point (2) in Section 8.1.1. However, the catalytic activity of the product in question is a consequence of its formation and not the converse. 

Different from conventional chemical kinetics, the rates in biochemical reactions networks are usually saturable hyperbolic functions. For an increasing substrate concentration, the rate increases only up to a maximal rate Vm, determined by the turnover number fccat = k2 and the total amount of enzyme Ej. The turnover number ca( measures the number of catalytic events per seconds per enzyme, which can be more than 1000 substrate molecules per second for a large number of enzymes. The constant Km is a measure of the affinity of the enzyme for the substrate, and corresponds to the concentration of S at which the reaction rate equals half the maximal rate. For S most active sites are not occupied. For S >> Km, there is an excess of substrate, that is, the active sites of the enzymes are saturated with substrate. The ratio kc.AJ Km is a measure for the efficiency of an enzyme. In the extreme case, almost every collision between substrate and enzyme leads to product formation (low Km, high fccat). In this case the enzyme is limited by diffusion only, with an upper limit of cat /Km 108 — 109M. v 1. The ratio kc.MJKm can be used to test the rapid... 

Despite the large amount of biochemical and structural studies of sirtuins in complex with various substrates, cofactors and reaction products, the catalytic mechanism of this class of enzymes is still a matter of debate. SN -like [56] and SN -like [60] mechanisms have been inferred from structural studies but further biochemical and possibly structural studies will be required to clarify which mechanism is used by sirtuins. It should also be noted that another matter of debate concerns the mode of noncompetitive inhibition of sirtuins by the reaction product nicotinamide [62], various structural studies having highlighted different binding pockets for this molecule [63, 64]. 

The petrochemical industry typically works on a build-up approach where the base oil feedstock is fractionated, and complex materials are built up from simpler ones, producing a wide array of materials in the process, for a range of market outlets. The future exploitation of plant materials is seen in a somewhat similar fashion, although in contrast to the petrochemical industry, there will typically be an initial breaking up of more complex materials into simpler building blocks that can then be utilised and built on with the support of chemical, biochemical and catalytic processes, to produce more complex products synonymous with those produced by today s petrochemical industry. This whole crop approach to industrial use of plant-derived material is typically termed biorefining (see Chapter 1). 

A major aspect of research and development in industrial catalysis is the identification of catalytic materials and reaction conditions that lead to effective catalytic processes. The need for efficient approaches to facilitate the discovery of new solid catalysts is particularly timely in view of the growing need to expand the applications of catalytic technologies beyond the current chemical and petrochemical industries. For example, new catalysts are needed for environmental applications such as treatment of noxious emissions or for pollution prevention. Improved catalysts are needed for new fuel cell applications. The production of high-value specialty chemicals requires the development of new catalytic materials. Furthermore, new catalysts may be combined with biochemical processes for the production of chemicals from renewable resources. The catalysts required for these new applications may be different from those in current use in the chemical and petrochemical industries. 

Asymmetric synthesis is the chemical or biochemical conversion of a prochiral substrate to a chiral product. In general, this involves reaction at an unsaturated site having prochiral faces (C=C, C=N, C=0, etc.) to give one product enantiomer in excess over another. The reagents effecting the asymmetric synthesis are used either catalytically or stoichiometrically. Oearly, the former is to be preferred, for economic reasons, when applicable. The reagents can be either chemical or enzymatic. 

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