Byproduct-free geraniol glycosylation by whole-cell biotransformation with recombinant Escherichia coli
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ORIGINAL RESEARCH PAPER
Byproduct-free geraniol glycosylation by whole-cell biotransformation with recombinant Escherichia coli Xenia Priebe . Manh Dat Hoang . Julian Ru¨diger . Maria Turgel . Julia Tro¨ndle . Wilfried Schwab . Dirk Weuster-Botz
Received: 17 March 2020 / Accepted: 18 August 2020 Ó The Author(s) 2020
Abstract Objective Geraniol, a fragrance of great importance in the consumer goods industry, can be glucosylated by the UDP-glucose-dependent glucosyltransferase VvGT14a from Vitis vinifera, yielding more stable geranyl glucoside. Escherichia coli expressing VvGT14a is a convenient whole-cell biocatalyst for this biotransformation due to its intrinsic capability for UDPglucose regeneration. The low water solubility and high cytotoxicity of geraniol can be overcome in a biphasic system where the non-aqueous phase functions as an in situ substrate reservoir. However, the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10529-020-02993-z) contains supplementary material, which is available to authorized users. X. Priebe M. D. Hoang M. Turgel J. Tro¨ndle D. Weuster-Botz (&) Department of Mechanical Engineering, Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstr. 15, 85748 Garching, Germany e-mail: [email protected] Present Address: X. Priebe Bioprocess Technology, Evonik Operations GmbH, Rodenbacher Chaussee 4, 63457 Hanau-Wolfgang, Germany
effect of different process variables on the biphasic whole-cell biotransformation is unknown. Thus, the goal of this study was to identify potential bottlenecks during biotransformation with in situ geraniol supply via isopropyl myristate as second non-aqueous phase. Results First, insufficient UDP-glucose supply could be ruled out by measurement of intracellular UDPglucose concentrations. Instead, oxygen supply was determined as a bottleneck. Moreover, the formation of the byproduct geranyl acetate by chloramphenicol acetyltransferase (CAT) was identified as a constraint for high product yields. The use of a CAT-deficient whole-cell biocatalyst prevented the formation of geranyl acetate, and geranyl glucoside could be obtained with 100% selectivity during a biotransformation on L-scale. Conclusion This study is the first to closely analyze the whole-cell biotransformation of geraniol with Escherichia coli expressing an UDP-glucose-dependent glucosyltransferase and can be used as an optimal starting point for the design of other glycosylation processes. Keywords Whole-cell biocatalysis Glucosyltransferase Biphasic system Geraniol UDP-glucose
J. Ru¨diger W. Schwab School of Life Sciences Weihenstephan, Biotechnology of Natural Products, Technical University of Munich, LieselBeckmann-Str. 1, 85354 Freising, Germany
123
Biotechnol Lett
Introduction Glycosylation is a valuable method for increasing the shelf life of volatile fragrance compounds contained in cosmetic and household products (Schwab et al. 2015). A fragran
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