Immobilization of ω-transaminases by encapsulation in a sol-gel/celite matrix
Research Centre Applied Biocatalysis, c/o Department of Chemistry, Organic and Bioorganic Chemistry, University of Graz, Heinrichstrasse 28, A-8010 Graz, AustriaJournal of Molecular Catalysis B Enzymatic (Impact Factor: 2.13). 04/2010; 63(1-2):39-44. DOI: 10.1016/j.molcatb.2009.12.001
Commercially available ω-transaminases ω-TA-117, -113, and Vibrio fluvialis (Vf-AT) have been immobilized in a sol-gel matrix. Improved results were obtained by employing Celite 545 as additive. The immobilized ω-transaminases ω-TA-117, -113, and V. fluvialis (Vf-AT) were tested in the kinetic resolution of α-chiral primary amines. In contrast to the free enzyme ω-TA-117, the sol-gel/celite immobilized enzyme showed activity even at pH 11. Recycling of the sol-gel/Celite 545 immobilized ω-transaminase ω-TA-117 was performed over five reaction cycles without any substantial loss in enantioselectivity and conversion. Finally, the immobilized ω-TA 117 was employed in a one-pot two-step deracemization of rac-mexiletine and rac-4-phenyl-2-butylamine, two pharmacologically relevant amines. The corresponding optically pure (S)-amines were obtained in up to 95% isolated yield (>99% ee).
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- "Whole cells containing -TAs were immobilized in calcium alginate beads by Shin and Kim , and by Martin et al. . Encapsulation of -transaminases in a sol–gel/celite matrix was reported by Koszelewski et al. . The covalent immobilization of -transaminase from Vibrio fluvialis was investigated by Yi et al. using chitosan, Eupergit C ® and Tentagel S COOSu . "
ABSTRACT: Production of chiral amines using ω-transaminases has been thoroughly studied in recent years. Immobilized ω-transaminases, however, have been used on relatively few occasions despite potential benefits such as reuse of enzyme and ease of product purification. In this study principally different methods including surface immobilization, entrapment and sweep flocculation using titanium oxide, Ca-alginate and chitosan respectively were evaluated for the immobilization of recombinant Escherichia coli cells. The enzyme expressed was a modified Arthrobacter citreus ω-transaminase with improved thermostability. The preparations were compared in terms of cell loading capacity, operational stability in repeated batches and storage stability using the conversion of methylbenzylamine to acetophenone.The use of chitosan for cell immobilization proved to be the method of choice since it was both very simple and effective. At a very high cell loading of 3.2 g cells/g chitosan >60% activity was observed. The preparation was reused in eight successive 1-h batches with >90% remaining activity. To further demonstrate its usability the preparation was used for asymmetric synthesis of (S)-4′-cyano-(α)-methylbenzylamine in three repeated bathes (cycle time >20 h), using isopropylamine as the amine donor. Storage stability was comparable with that of non-immobilized cells. It was concluded that the chitosan method due to its properties and simplicity would be advantageous for use also on a larger scale.PROCESS BIOCHEMISTRY 07/2012; 47(7):1129–1134. DOI:10.1016/j.procbio.2012.04.013 · 2.52 Impact Factor
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- "Celite acts as an additive in sol–gel matrix for ω-transaminases immobilization. It has been preferred due to its chemical inertness and interconnected pore structure (Koszelewski et al. 2010). "
ABSTRACT: The current demands of the world’s biotechnological industries are enhancement in enzyme productivity and development of novel techniques for increasing their shelf life. These requirements are inevitable to facilitate large-scale and economic formulation. Enzyme immobilization provides an excellent base for increasing availability of enzyme to the substrate with greater turnover over a considerable period of time. Several natural and synthetic supports have been assessed for their efficiency for enzyme immobilization. Nowadays, immobilized enzymes are preferred over their free counterpart due to their prolonged availability that curtails redundant downstream and purification processes. Future investigations should endeavor at adopting logistic and sensible entrapment techniques along with innovatively modified supports to improve the state of enzyme immobilization and provide new perspectives to the industrial sector.02/2012; 3(1). DOI:10.1007/s13205-012-0071-7
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ABSTRACT: This paper addresses the problem of resource allocation in a general multiple access scenario. Powers are supposed to be fixed and maximization of the bit rate is put as an objective, with a number of fairness constraints that provide each user with individual bit rates in proportion with their needs. Linear programming algorithms give the solution for the matched filter bound. As soon as the channels are frequency-selective, the use of joint detectors is proposed. An adapted allocation algorithm is given, that implies the update of the joint detector performance for each iteration. A fast update algorithm is also proposed. Results are given for a 5-user powerline access networkCommunications and Vehicular Technology, 2000. SCVT-200. Symposium on; 02/2000
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