Directional bioconversion and optimization of stevioside into rubusoside
by Lelliottia sp. LST-1
Abstract
Steviol glycosides, mostly extracted from Stevia rebaudiana Bertoni, are
non-caloric, safe natural sweeteners. Steviosides make up more than 50%
of total steviol glycosides but possess a bitter aftertaste, which
limits their application as food additives. Trace amounts of rubusosides
are acceptable sweeteners, but their supply is limited. In this study,
we screened an endophytic bacteria (Lelliottia LST-1) that can
specifically convert stevioside into rubusoside and reach a conversion
rate of 75.4% after response surface optimization. Potential
β-glucosidases GH3-1, GH3-2, GH3-3, and GH3-4 based on whole genome
sequencing were expressed and interacted with steviol glycosides to
explore principle and process of biological transformation.
High-performance liquid chromatography revealed that all enzymes
hydrolyzed stevioside and generated rubusoside, but substrate
specificity analysis indicated that GH3-2 is the most suitable choice
for the durative, steady, and high-efficiency production of rubusoside