Biocatalysis Subject

The role of biocatalysis in two-phase systems has many parallels with the subject we have covered under extractive reactions. It appears that a two-phase system was originally considered for transformations of water insoluble substances like steroids. Now, a series of treatises are available which teach us that the maximum value of the apparent equilibrium constant for a second-order reaction in a two-phase system can exceed the equilibrium... 

Many reported biotransformations are initially only demonstrated on a very small scale, the substrates or products may be subject to competing reactions if other enzymes are present (this can be a serious issue in whole-cell biocatalysis), or the desired enzyme is insufficiently active or produced in low levels. For many biotransformations a little care and attention is needed in the growth of the microbe to achieve the desired results. Production of a specific enzyme from a microbe can often be increased by growing the cells in the presence of a very small concentration (typically micromolar) of an inducer. The inducer could be a natural enzyme substrate, a substrate mimic or a molecule which is in some way associated with a substrate s availability or role in metabolism. This process is called induction and represents a genetic switch which cells use to respond... 

Biocatalysis in ionic liquids was first reported in 2000 [7, 8, 9]. The early work involved ionic liquids composed of a 1,3-dialkylimidazolium or N-alkylpyridinium cation and a weakly-coordinating anion (Figure 10.1). More recently, attention is shifting toward new structural types. A number of reviews of this rapidly expanding subject have appeared [10, 11, 12, 13, 14]. 

This short review deals with the topical subject chirality in bioorganosilicon chemistry . Two different aspects will be discussed (i) biological recognition of enantiomeric organosilicon drugs and (ii) biocatalysis as a method for the preparation of optically active organosilicon compounds . Most of the experimental material described in this article (which does not lay claim to completeness) comes from our own laboratory. 

This chapter outlines the principles of green chemistry, and explains the connection between catalysis and sustainable development. It covers the concepts of environmental impact, atom economy, and life-cycle analysis, with hands-on examples. Then it introduces the reader to heterogeneous catalysis, homogeneous catalysis, and biocatalysis, explaining what catalysis is and why it is important. The last two sections give an overview of the tools used in catalysis research, and a list of recommended books on specialized subjects in catalysis. 

As evident from the above discussion, ILs have emerged as alternative solvent systems for biocatalysis which has already established with a range of different class of enzymes performing better or at least comparable to conventional orgattic solvents. The added advantages of easy work up procedure, possibility of recycling the solvent and multiple uses of enzymes were also noted. However, the complexity in the nature of ILs has resulted variation in enzyme performance in terms of reaction rate and enantioselectivity. A brief comparative analysis of enzyme activity versus nature of the component of ILs would be helpful for better understanding of the subject and careful selection of ILs for a desired reaction. 

The last two decades have seen an explosion of interest in ionic liquids [1]. Their use as solvents has been the subject of widespread academic study [2] and they have been applied in a number of commercial processes [3]. Much of the interest in ionic liquids has centered on their possible use as green solvents [4]. However, this has been the subject of much controversy [5], and the concept of a green solvent itself is now somewhat dated. There have been many reviews of ionic liquids. Some of these have focused on particular applications, for example, analysis [6], biocatalysis [7], catalysis [8], electrochemical devices [9], or engineering fluids [10]. Others have concentrated on particular subgroups of ionic liquids, for example, task-specific ionic liquids [11]. This chapter summarizes what is known about the physicochemical properties that are of particular interest for supported ionic hquid phases (SILPs). 

This is the most common application of biocatalysis in organic synthesis and represents the majority of published examples. Enzymes that catalyze acyl transfer reactions of esters and amides are widely distributed in nature and belong to the lipase/esterase and protease/amidase families, respectively. They play key roles in the metabolism of lipids and proteins and the choice of names, lipase versus esterase, is subject to debate. Normally, acyl ttansfer occurs almost exclusively to water, resulting in hydrolysis. This is particularly valuable for amide hydrolysis that normally requires forcing conditions and strong acid or... 

Subjects LCSH Enzymes-Biotechnology. Biocatalysis. Green chemistry. BISAC TECHNOLOGY ENGINEERING /... 

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