Stevioside is a novel sweeter which is extracted from stevia leaves, and the
stevioside in the stevia leaves mainly comprises two components of
stevioside and
rebaudioside A. The
sweetness and
mouthfeel of the
rebaudioside A are both excellent, while the
stevioside has certain lingering bitterness; and as the structure and nature of the
rebaudioside A are approximate to the structure and nature of the stevioside, the separation of rebaudioside A and stevioside features high cost and great technical difficulty. In the invention, microorganisms are transformed for 20h-150h under the conditions that the concentration of the stevioside is 0.01%-5% (W / W), the temperature is 25-80 DEG C, the quantity of inverting
enzyme or bacterial solution is 0.1%-10% (W / W), and the pH value is 2.0-7.0, and the stevioside contained in the rebaudioside A solution can be selectively degraded, thus obtaining high purity rebaudioside A containing no stevioside. The
biotransformation method used in the invention has temperate conditions, does not use toxic
methanol and other chemicals or
macroporous resin with high cost, thus being a novel technology with safety, greenness and environmental friendliness.