Bioconversion of Stevioside to Rebaudioside E Using Glycosyltransferase UGTSL2

Area of Science:

• Biotechnology
• Enzymology
• Natural Product Synthesis

Background:

• Rebaudioside E is a minor steviol glycoside, known as a high-intensity sweetener.
• It serves as a precursor for next-generation stevia sweeteners like Rebaudioside D and M.
• Current production methods for steviol glycosides can be limited.

Purpose of the Study:

• To develop a novel enzymatic synthesis for Rebaudioside E.
• To explore the potential of UDP-glucosyltransferase UGTSL2 and sucrose synthase StSUS1 in steviol glycoside modification.
• To optimize the bioconversion of stevioside into Rebaudioside E.

Main Methods:

• Enzymatic synthesis using UDP-glucosyltransferase UGTSL2 (from Solanum lycopersicum) and sucrose synthase StSUS1 (from Solanum tuberosum).
• Analysis of regioselectivity and stereoselectivity of the enzymatic glucosylation reaction.
• Verification of Rebaudioside E production using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS).

Main Results:

• Enzymatic synthesis successfully produced Rebaudioside E from stevioside.
• The main product was identified as Rebaudioside E, with a (β1→2) linkage formed.
• A high yield of 15.92 g/l Rebaudioside E was achieved in a 24-hour bioconversion reaction.

Conclusions:

• Enzymatic synthesis using UGTSL2 and StSUS1 is an effective method for producing Rebaudioside E.
• This method offers a potential route for the efficient biosynthesis of next-generation stevia sweeteners.
• The study demonstrates the utility of specific plant enzymes in modifying steviol glycosides.