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

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-?N, and in particular its Q1140E-mutant, efficiently ?-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(?1?C-19 residue of RebA, with the initial formation of an (?1?6) linkage. Docking of RebA in the active site of the enzyme revealed that only the steviol C-19 ?-D-glucosyl moiety is available for glucosylation. Response surface methodology was applied to optimize the Gtf180-?N-Q1140E-catalyzed ?-glucosylation of RebA, resulting in a highly productive process with a RebA conversion of 95% and a production of 115?g/L ?-glucosylated products within 3?h. Development of a fed-batch reaction allowed further suppression of ?-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-?N-Q1140E glucansucrase mutant enzyme thus is an efficient biocatalyst for generating ?-glucosylated RebA variants with improved edulcorant/organoleptic properties.

SUBMITTER: Te Poele EM 

PROVIDER: S-EPMC5784128 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature