Highly efficient production of rare sugars D‐psicose and L‐tagatose by two engineered D‐tagatose epimerases. Issue 2 (20th August 2015)

• Record Type: Journal Article
• Authors: Bosshart, Andreas; Wagner, Nina; Lei, Lei; Panke, Sven; Bechtold, Matthias
• Is Part Of: Biotechnology and bioengineering. Volume 113:Issue 2(2016)
• Page Start: 349
• Page End: 358
• Publication Date: 2015-08-20
• Subjects: Directed evolution -- d‐tagatose epimerase -- improving catalytic activity -- rare monosaccharides -- enzyme membrane reactor -- enzyme engineering; Biotechnology -- Periodicals; Bioengineering -- Periodicals; 660.6
• DOI: 10.1002/bit.25547
• Languages: English
• ISSNs: 0006-3592

Abstract

ABSTRACT: Rare sugars are monosaccharides that do not occur in nature in large amounts. However, many of them demonstrate high potential as low‐calorie sweetener, chiral building blocks or active pharmaceutical ingredients. Their production by enzymatic means from broadly abundant epimers is an attractive alternative to synthesis by traditional organic chemical means, but often suffers from low space‐time yields and high enzyme costs due to rapid enzyme degradation. Here we describe the detailed characterization of two variants ofd ‐tagatose epimerase under operational conditions that were engineered for high stability and high catalytic activity towards the epimerization ofd ‐fructose tod ‐psicose andl ‐sorbose tol ‐tagatose, respectively. A variant optimized for the production ofd ‐psicose showed a very high total turnover number (TTN) of up to 10 8 catalytic events over a catalyst's lifetime, determined under operational conditions at high temperatures in an enzyme‐membrane reactor (EMR). Maximum space‐time yields as high as 10.6 kg L −1 d −1 were obtained with a small laboratory‐scale EMR, indicating excellent performance. A variant optimized for the production ofl ‐tagatose performed less stable in the same setting, but still showed a very good TTN of 5.8 × 10 5 and space‐time yields of up to 478 g L −1 d −1 . Together, these results confirm that large‐scale enzymatic access to rare sugars is feasible. Biotechnol. Bioeng. 2016;113: 349–358. © 2015 Wiley Periodicals, Inc. Abstract : Two different engineered D‐tagatose epimerase variants for the production of D‐psicose or L‐tagatose were generated and analyzed in terms of productivity and total turnover number at different temperatures. These variants showed total turnover numbers of up to 10 8 and specific productivities of up to 2.7 kg g −1 h −1, confirming their value for the synthesis of rare monosaccharides from cheap starting substrates.