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Open AccessArticle Engineering Cofactor Preference of Ketone Reducing Biocatalysts: A Mutagenesis Study on a γ-Diketone Reductase from the Yeast Saccharomyces cerevisiae Serving as an Example

by Michael Katzberg, Nàdia Skorupa-Parachin, Marie-Françoise Gorwa-Grauslund and Martin Bertau

Int. J. Mol. Sci. 2010, 11(4), 1735-1758; doi:10.3390/ijms11041735

Received: 23 February 2010 / Revised: 24 March 2010 / Accepted: 6 April 2010 / Published: 14 April 2010

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Abstract

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

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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. Full article

(This article belongs to the Special Issue Biocatalysis)

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Open AccessArticle Fructose Production by Inulinase Covalently Immobilized on Sepabeads in Batch and Fluidized Bed Bioreactor

by Emanuele Ricca, Vincenza Calabrò, Stefano Curcio, Alessandra Basso, Lucia Gardossi and Gabriele Iorio

Int. J. Mol. Sci. 2010, 11(3), 1180-1189; doi:10.3390/ijms11031180

Received: 13 January 2010 / Accepted: 17 March 2010 / Published: 19 March 2010

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Abstract

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

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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. Full article

(This article belongs to the Special Issue Biocatalysis)

Open AccessArticle Covalent Anchoring of Chloroperoxidase and Glucose Oxidase on the Mesoporous Molecular Sieve SBA-15

by Dirk Jung, Carsten Streb and Martin Hartmann

Int. J. Mol. Sci. 2010, 11(2), 762-778; doi:10.3390/ijms11020762

Received: 4 January 2010 / Revised: 9 February 2010 / Accepted: 9 February 2010 / Published: 24 February 2010

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Abstract

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

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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. Full article

(This article belongs to the Special Issue Biocatalysis)

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Open AccessReview Miniaturization in Biocatalysis

by Pedro Fernandes

Int. J. Mol. Sci. 2010, 11(3), 858-879; doi:10.3390/ijms11030858

Received: 7 January 2010 / Revised: 8 February 2010 / Accepted: 9 February 2010 / Published: 2 March 2010

Cited by 56 | PDF Full-text (218 KB) | HTML Full-text | XML Full-text

Abstract

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

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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. Full article

(This article belongs to the Special Issue Biocatalysis)

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Review

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Guest Editor Prof. Dr. Martin Hartmann Erlangen Catalysis Resource Center, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany E-Mail
Editorial Advisor Prof. Dr. Uwe T. Bornscheuer Institute of Biochemistry, Department of Biotechnology & Enzyme Catalysis, Greifswald University, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany Website \| E-Mail Fax: +49 (0)3834 86 80066 Interests: biocatalysis; protein engineering; high-throughput screening; enantioselective synthesis