Biocatalysis scale

The term biotransformation or biocatalysis is used for processes in which a starting material (precursor) is converted into the desired product in just one step. This can be done by use either of whole cells or of (partially) purified enzymes. Product examples range from bulk chemicals (such as acrylamide) to fine chemicals and chiral synthons (chiral amines or alcohols, for example). There are several books and reviews dealing with the use of bio transformations either at laboratory or at industrial scales [1, 10-13]. 

Nowadays biocatalysis is a well-assessed methodology that has moved from the original status of academic curiosity to become a widely exploited technique for preparative-scale reactions, up to the point that the so-called industrial biotechnology (to which biocatalysis contributes to the most extent) is one of the three pillars of the modern sustainable chemistry. 

In this volume not all stress types are treated. Various aspects have been reviewed recently by various authors e.g. The effects of oxygen on recombinant protein expression by Konz et al. [2]. The Mechanisms by which bacterial cells respond to pH was considered in a Symposium in 1999 [3] and solvent effects were reviewed by de Bont in the article Solvent-tolerant bacteria in biocatalysis [4]. Therefore, these aspects are not considered in this volume. Influence of fluid dynamical stresses on micro-organism, animal and plant cells are in center of interest in this volume. In chapter 2, H.-J. Henzler discusses the quantitative evaluation of fluid dynamical stresses in various type of reactors with different methods based on investigations performed on laboratory an pilot plant scales. S. S. Yim and A. Shamlou give a general review on the effects of fluid dynamical and mechanical stresses on micro-organisms and bio-polymers in chapter 3. G. Ketzmer describes the effects of shear stress on adherent cells in chapter 4. Finally, in chapter 5, P. Kieran considers the influence of stress on plant cells. 

However, the transfer of this technology from laboratory to industrial scale requires advances in the engineering of biocatalysis environment, particularly when one or more components are poorly water soluble [5-8]. 

D.M. York and T.-S. Lee (eds.), Multi-scale Quantum Models for Biocatalysis, 21-55. 

Ran, N., Zhao, T., Chen, Z. and Tao, J. (2008) Recent applications of biocatalysis in developing green chemistry for chemical synthesis at industrial scale. Green Chemistry, 10, 361-372. 

With biocatalysis becoming increasingly accepted in synthetic organic chemistry on both the laboratory and industrial scale, there is a huge need for new complexes that can utilize electrons or hydrogen as redox equivalents in cofactor reduction. These redox equivalents are very inexpensive, readily available, and produce no side products, which in turn significantly facilitates the downstream processing of products. 

Although the focus here is on the integration of biocatalysis with chemocataly-sis (bio-chemo cascades) for carbohydrates as renewable feedstocks, some representative examples (from laboratory to industrial scale) of both bio-bio and chemo-chemo cascades are also given below for comparison of their relative scope and limitations. 

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... 

---