Development of a multiphase reaction system for integrated synthesis of isomaltose with a new glucosyltransferase variant

Abstract

A new genetically derived variant of the glucosyltransferase from Streptococcus oralis has been characterized physicochemically and kinetically. Compared with the industrially used glucosyltransferase from Leuconostoc mesenteroides, the enzyme variant GTF-R S628D possesses 25 times higher affinity for the specific glucosylation of glucose. For a concept of integrated reaction and product isolation, a fluidized bed reactor with in situ product removal was applied. The technical feasibility and the applicability of the kinetic models for reaction and adsorption could be demonstrated. The immobilized enzyme was stable (20% activity loss after 192 h) and product could be obtained with 90% purity. A bioprocess model was generated which allowed the integral assessment of the enzymatic synthesis and in situ product adsorption. The model is a powerful tool which assists with the localization of optimal process parameters. It was applied for the process evaluation of other glucosyltransferases and demonstrated key characteristics of each enzymatic system.

Keywords::

• Glucosyltransferase
• in situ product removal
• modeling
• zeolite

Acknowledgements

This work is embedded in the collaborative research center SFB 578 ‘Development of biotechnological processes by integrating genetic and engineering methods – From gene to product’. The authors acknowledge the financial support provided by the German Research Foundation (DFG) and thank the collaborators (especially Dipl.-Biotechnol. Manuel Holtkamp for assistance with the reactor set-up) for their combined efforts and helpful discussions. We are very thankful to Wolfgang Grassl and Prof. Siegmund Lang (both of the Institute of Biochemistry and Biotechnology, TU Braunschweig) for placing fermentation equipment at our disposal.

This paper was first published as an Early Online Article on 8 December 2009.