Glucansucrase (mutant) enzymes from Lactobacillus reuteri 180 efficiently transglucosylate Stevia component rebaudioside A, resulting in a superior taste

Evelien M Te Poele, Tim Devlamynck, Manuel Jäger, Gerrit J Gerwig, Davy Van de Walle, Koen Dewettinck, Anna K H Hirsch, Johannis P Kamerling, Wim Soetaert, Lubbert Dijkhuizen

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Abstract

Steviol glycosides from the leaves of the plant Stevia rebaudiana are high-potency natural sweeteners but suffer from a lingering bitterness. The Lactobacillus reuteri 180 wild-type glucansucrase Gtf180-ΔN, and in particular its Q1140E-mutant, efficiently α-glucosylated rebaudioside A (RebA), using sucrose as donor substrate. Structural analysis of the products by MALDI-TOF mass spectrometry, methylation analysis and NMR spectroscopy showed that both enzymes exclusively glucosylate the Glc(β1→C-19 residue of RebA, with the initial formation of an (α1→6) linkage. Docking of RebA in the active site of the enzyme revealed that only the steviol C-19 β-D-glucosyl moiety is available for glucosylation. Response surface methodology was applied to optimize the Gtf180-ΔN-Q1140E-catalyzed α-glucosylation of RebA, resulting in a highly productive process with a RebA conversion of 95% and a production of 115 g/L α-glucosylated products within 3 h. Development of a fed-batch reaction allowed further suppression of α-glucan synthesis which improved the product yield to 270 g/L. Sensory analysis by a trained panel revealed that glucosylated RebA products show a significant reduction in bitterness, resulting in a superior taste profile compared to RebA. The Gtf180-ΔN-Q1140E glucansucrase mutant enzyme thus is an efficient biocatalyst for generating α-glucosylated RebA variants with improved edulcorant/organoleptic properties.

Original languageEnglish
Article number1516
Number of pages12
JournalScientific Reports
Volume8
Issue number1
DOIs
Publication statusPublished - 24-Jan-2018

Keywords

  • Glucansucrase enzymes
  • Lactobacillus reuteri 180
  • Stevia
  • rebaudioside A
  • mutant enzymes
  • ENZYMATIC TRANSGLUCOSYLATION
  • STRUCTURAL-CHARACTERIZATION
  • STEVIOSIDE
  • SWEET
  • GTF180
  • GLYCOSIDES
  • RUBUSOSIDE
  • REBAUDIANA
  • GLUCAN
  • CYCLODEXTRIN

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