Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Record number 357532
Title Microbial alcohol dehydrogenases: identification, characterization and engineering
Author(s) Machielsen, M.P.
Source Wageningen University. Promotor(en): John van der Oost; Willem de Vos. - [S.l.] : S.n. - ISBN 9789085047100 - 136
Department(s) Microbiology
Publication type Dissertation, internally prepared
Publication year 2007
Keyword(s) alcohol dehydrogenase - aminozuursequenties - genetische modificatie - industriële microbiologie - alcohol dehydrogenase - amino acid sequences - genetic engineering - industrial microbiology
Categories Industrial Microbiology
Abstract Keywords: alcohol dehydrogenase, laboratory evolution, rational protein engineering, Pyrococcus furiosus, biocatalysis, characterization, computational design, thermostability. Alcohol dehydrogeases (ADHs) catalyze the interconversion of alcohols, aldehydes and ketones. They display a wide variety of substrate specificities and are involved in an astonishingly wide range of metabolic processes, in all living organisms. Besides the scientific interest in ADHs, they are also attractive biocatalysts for industrial applications. Especially, their capability to catalyze chemo-, stereo-, and region-selective reactions endows them with considerable potential for a range of applications in food, pharmaceutical and fine chemicals industries. Natural enzymes are, however, optimized and often highly specialized for certain biological functions; hence, in many instances natural enzymes do not perform optimally in an industrial process. Laboratory evolution (random methods) and/or rationale-based protein engineering (design methods) can be applied to obtain enzyme variants, which are suitable for a particular industrial application. This study describes the identification, characterization and engineering of microbial ADHs. Because protein stability is an important issue for in vitro applications, thermophiles are considered a potential source of thermozymes. The genes coding for sixteen putative ADHs were identified in the genome of the hyperthermophilic archaeon Pyrococcus furiosus and a more detailed level of function prediction was attempted for all identified genes. Subsequently, fifteen of the putative ADHs were heterologously produced and an initial screening for activities was performed in which two of the putative ADHs showed activities. Next, these two ADHs, AdhD and Pf-TDH, were purified and characterized. AdhD is a member of the aldo-keto reductase superfamily and Pf-TDH is a l-threonine dehydrogenase. In addition, either laboratory evolution or rationale protein engineering was applied to improve the properties of two selected ADHs to extend their potential for industrial applications. AdhA, a thermostable ADH of P. furiosus, was engineered by laboratory evolution to improve the production of (2S,5S)-hexanediol at moderate temperatures. High-resolution 3D structures are required to perform the directed engineering of proteins. The ADH of Lactobacillus brevis (Lb-ADH) was selected because a 1.0 Å resolution structure was available, and because of its potential for industrial application. Structure-based computational protein engineering was applied to adjust its cofactor specificity.
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