科研之友
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摘要
Production of chiral amines using omega-transaminases has been thoroughly studied in recent years. Immobilized w-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 omega-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. %26lt;br%26gt;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 %26gt;60% activity was observed. The preparation was reused in eight successive 1-h batches with %26gt;90% remaining activity. To further demonstrate its usability the preparation was used for asymmetric synthesis of (S)-4%26apos;-cyano-(alpha)-methylbenzylamine in three repeated bathes (cycle time %26gt;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.
- 出版日期2012-7
