Monk fruit extracts containing mogrol glycosides such as mogroside V may be treated with enzymes under specific reaction conditions to shift distribution of the Siamenoside I reaction product. Modified enzymes are also employed to shift Siamenoside I distribution to increase yield of Siamenoside I and reduce reaction contaminants. Methods of purifying bioconversion reaction product are also described. Siamenoside I obtained using these methods is a useful sweetener and flavor enhancer for food and beverage compositions and the like.