Bioconversion of Stevioside to Rebaudioside E Using Glycosyltransferase UGTSL2
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Bioconversion of Stevioside to Rebaudioside E Using Glycosyltransferase UGTSL2 Liangliang Chen 1 & Huayi Pan 1 & Ruxin Cai 1 & Yan Li 1 & Honghua Jia 1 & Kequan Chen 1 & Ming Yan 1 & Pingkai Ouyang 1 Received: 3 April 2020 / Accepted: 29 September 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Rebaudioside E, one of the minor components of steviol glycosides, was first isolated and identified from Stevia rebaudiana in 1977. It is a high-intensity sweetener that tastes about 150–200 times sweeter than sucrose and is also a precursor for biosynthesis of rebaudioside D and rebaudioside M, the next-generation Stevia sweeteners. In this work, new unknown steviol glycosides were enzymatically synthesized from stevioside by coupling UDP-glucosyltransferase UGTSL2 from Solanum lycopersicum and sucrose synthase StSUS1 from Solanum tuberosum. Rebaudioside E was speculated to be the main product of glucosylation of the Glc(β1→C-19) residue of stevioside along with the formation of a (β1→2) linkage based on the analysis of the regioselectivity and stereoselectivity of UGTSL2, and verified afterwards by LC-MS/MS with standard. In a 20-ml bioconversion reaction of 20 g/l stevioside by UGTSL2 and StSUS1, 15.92 g/l rebaudioside E was produced for 24 h. Keywords Bioconversion . Glucosyltransferase . Steviol glycoside . Rebaudioside E . Stevioside
Introduction Steviol glycosides (SGs), natural sweeteners from the leaves of Stevia rebaudiana that are used to reduce the contribution of sucrose and other high-energy sweeteners to excessive human calorie intake, have attracted increasing interest [1, 2]. In addition to their intense sweetness and low- and zero-calorie value, these compounds also possess anti-hyperglycemic, antihypertensive, anti-inflammatory, antitumor, and immunomodulatory properties [3, 4]. Different numbers and types of sugars attached to the steviol C-13 hydroxyl and/or C-19 carboxylic acid functional group distinctly contribute to the diversity of SGs (Table 1) and affect their taste [5]. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12010-02003439-y) contains supplementary material, which is available to authorized users.
* Yan Li [email protected] Extended author information available on the last page of the article
Applied Biochemistry and Biotechnology Table 1 Chemical structures and sources of representative steviol glycosides and their derivatives
Steviol glycoside
Chemical structure R1
R2
Stevioside Rebaudioside A
glcβ1glcβ1-
glcβ1–2glcβ1glcβ1–2(glcβ1–3) glcβ1-
Rebaudioside B
H
glcβ1–2(glcβ1–3) glcβ1-
Rebaudioside C
glcβ1-
Rebaudioside D
glcβ1–2glcβ1-
rhaα1–2(glcβ1–3) glcβ1glcβ1–2(glcβ1–3) glcβ1-
Rebaudioside D2
glcβ1–6glcβ1-
Rebaudioside E Rebaudioside F
glcβ1–2glcβ1glcβ1-
Rebaudioside I
glcβ1–3glcβ1-
Rebaudioside M
glcβ1–2(glcβ1–3) glcβ1-
glcβ1–2(glcβ1–3) glcβ1-
Rebaudioside M2
glcβ1–2(glcβ1–6) glcβ1-
glcβ1–2(glcβ1–3) glcβ1-
Rebaudioside T
xylβ1–2(glcβ1–3) glcβ1araα1–6glcβ1-
glcβ1–2(gl
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