Cloning, expression, and one-step purifcation/immobilization of two carbohydrate-binding module-tagged alcohol dehydrogenases

Abstract

Background: The feasibility of biochemical transformation processes is usually greatly dependent on biocatalysts cost. Therefore, immobilizing and reusing biocatalysts is an approach to be considered to bring biotransformations closer to industrial feasibility, since it does not only allow to reuse enzymes but can also improve their stability towards several reaction conditions. Carbohydrate-Binding Modules (CBM) are well-described domains involved in substrate binding which have been already used as purifcation tags.

Results: In this work, two diferent Carbohydrate-Binding Modules (CBM3 and CBM9) have been successfully fused to an alcohol dehydrogenase from Saccharomyces cerevisiae, which has been produced in bench-scale reactor using an auxotrophic M15-derived E. coli strain, following a fed-batch strategy with antibiotic-free medium. Around 40mg·g−1 DCW of both fusion proteins were produced, with a specifc activity of >65AU·mg−1 . Overexpressed proteins were bound to a low-cost and highly selective cellulosic support by one-step immobilization/purifcation process at >98% yield, retaining about a 90% of initial activity. Finally, the same support was also used for protein purifcation, aiming to establish an alternative to metal afnity chromatography, by which CBM9 tag proved to be useful, with a recovery yield of >97% and 5-fold increased purity grade.

Conclusion: CBM domains were proved to be suitable for one-step immobilization/purifcation process, retaining almost total activity ofered. However, purifcation process was only successful with CBM9.