http://www.mdpi.com/journal/ijms/special_issues/biocatalysis/ Dear Colleagues, Biocatalysis encompasses the use of enzymes or whole cell systems for the conversion of readily available, inexpensive starting materials to high value products. Enzymes frequently display extraordinary chemo-, enantio- or regioselectivity, making them attractive catalysts for a wide range of chemical transformations. Enzymes typically operate under mild conditions of pH and temperature and often are compatible to each other. As a result of these advantages, enzymes and whole cells are increasingly applied in areas ranging from the production of intermediates for pharmaceuticals, fine chemicals, agrichemicals, biofuels and performance chemicals. In the light of the increasing importance of biocatalysis, the International Journal of Molecular Science will publish a special issuecovering both fundamental aspects of biocatalysis and advances in industrial applications. Reviews and original papers are welcome and will be considered for publication. Possible Topics include (but are not limited to) directed molecular evolution of enzymes, enzyme discovery and high-throughput screening, enzyme optimization, stabilization and immobilization, new types of reaction transformations, industrial application of enzymes including utilization of biomass, process development and reaction engineering. Prof. Dr. Martin Hartmann Guest Editor {snippet name="submission_info"} http://www.mdpi.com/1422-0067/11/4/1735/ The synthesis of pharmaceuticals and catalysts more and more relies on enantiopure chiral building blocks. These can be produced in an environmentally benign and efficient way via bioreduction of prochiral ketones catalyzed by dehydrogenases. A productive source of these biocatalysts is the yeast Saccharomyces cerevisiae, whose genome also encodes a reductase catalyzing the sequential reduction of the γ-diketone 2,5-hexanedione furnishing the diol (2S,5S)-hexanediol and the γ-hydroxyketone (5S)-hydroxy-2-hexanone in high enantio- as well as diastereoselectivity (ee and de >99.5%). This enzyme prefers NADPH as the hydrogen donating cofactor. As NADH is more stable and cheaper than NADPH it would be more effective if NADH could be used in cell-free bioreduction systems. To achieve this, the cofactor binding site of the dehydrogenase was altered by site-directed mutagenesis. The results show that the rational approach based on a homology model of the enzyme allowed us to generate a mutant enzyme having a relaxed cofactor preference and thus is able to use both NADPH and NADH. Results obtained from other mutants are discussed and point towards the limits of rationally designed mutants. http://www.mdpi.com/1422-0067/11/4/1735/ Wed, 14 Apr 2010 00:00:00 CEST International Journal of Molecular Sciences 2010-04-14 11 4 Article 1735 1758 1422-0067 Engineering Cofactor Preference of Ketone Reducing Biocatalysts: A Mutagenesis Study on a γ-Diketone Reductase from the Yeast Saccharomyces cerevisiae Serving as an Example 2010-04-14 doi: 10.3390/ijms11041735 Katzberg Skorupa-Parachin Gorwa-Grauslund Bertau http://www.mdpi.com/1422-0067/11/3/1180/ The present work is an experimental study of the performance of a recently designed immobilized enzyme: inulinase from Aspergillus sp. covalently immobilized on Sepabeads. The aim of the work is to test the new biocatalyst in conditions of industrial interest and to assess the feasibility of the process in a fluidized bed bioreactor (FBBR). The catalyst was first tested in a batch reactor at standard conditions and in various sets of conditions of interest for the process. Once the response of the catalyst to different operating conditions was tested and the operational stability assessed, one of the sets of conditions tested in batch was chosen for tests in FBBR. Prior to reaction tests, preliminary fluidization tests were realized in order to define an operating range of admissible flow rates. As a result, the FBR was run at different feed flow rates in a closed cycle configuration and its performance was compared to that of the batch system. The FBBR proved to be performing and suitable for scale up to large fructose production. http://www.mdpi.com/1422-0067/11/3/1180/ Fri, 19 Mar 2010 00:00:00 CET International Journal of Molecular Sciences 2010-03-19 11 3 Article 1180 1189 1422-0067 Fructose Production by Inulinase Covalently Immobilized on Sepabeads in Batch and Fluidized Bed Bioreactor 2010-03-19 doi: 10.3390/ijms11031180 Ricca Calabrò Curcio Basso Gardossi Iorio http://www.mdpi.com/1422-0067/11/3/858/ The use of biocatalysts for the production of both consumer goods and building blocks for chemical synthesis is consistently gaining relevance. A significant contribution for recent advances towards further implementation of enzymes and whole cells is related to the developments in miniature reactor technology and insights into flow behavior. Due to the high level of parallelization and reduced requirements of chemicals, intensive screening of biocatalysts and process variables has become more feasible and reproducibility of the bioconversion processes has been substantially improved. The present work aims to provide an overview of the applications of miniaturized reactors in bioconversion processes, considering multi-well plates and microfluidic devices, update information on the engineering characterization of the hardware used, and present perspective developments in this area of research. http://www.mdpi.com/1422-0067/11/3/858/ Tue, 02 Mar 2010 00:00:00 CET International Journal of Molecular Sciences 2010-03-02 11 3 Review 858 879 1422-0067 Miniaturization in Biocatalysis 2010-03-02 doi: 10.3390/ijms11030858 Pedro Fernandes http://www.mdpi.com/1422-0067/11/2/762/ Functionalization of porous solids plays an important role in many areas, including heterogeneous catalysis and enzyme immobilization. In this study, large-pore ordered mesoporous SBA-15 molecular sieves were synthesized with tetraethyl orthosilicate (TEOS) in the presence of the non-ionic triblock co-polymer Pluronic P123 under acidic conditions. These materials were grafted with 3 aminopropyltrimethoxysilane (ATS), 3-glycidoxypropyltrimethoxysilane (GTS) and with 3 aminopropyltrimethoxysilane and glutaraldehyde (GA-ATS) in order to provide covalent anchoring points for enzymes. The samples were characterized by nitrogen adsorption, powder X-ray diffraction, solid-state NMR spectroscopy, elemental analysis, diffuse reflectance fourier transform infrared spectroscopy and diffuse reflectance UV/Vis spectroscopy. The obtained grafted materials were then used for the immobilization of chloroperoxidase (CPO) and glucose oxidase (GOx) and the resulting biocatalysts were tested in the oxidation of indole. It is found that enzymes anchored to the mesoporous host by the organic moieties can be stored for weeks without losing their activity. Furthermore, the covalently linked enzymes are shown to be less prone to leaching than the physically adsorbed enzymes, as tested in a fixed-bed reactor under continuous operation conditions. http://www.mdpi.com/1422-0067/11/2/762/ Wed, 24 Feb 2010 00:00:00 CET International Journal of Molecular Sciences 2010-02-24 11 2 Article 762 778 1422-0067 Covalent Anchoring of Chloroperoxidase and Glucose Oxidase on the Mesoporous Molecular Sieve SBA-15 2010-02-24 doi: 10.3390/ijms11020762 Dirk Jung Carsten Streb Martin Hartmann