Review on D -Allulose: In vivo Metabolism, Catalytic Mechanism, Engineering Strain Construction, Bio-Production Technology

Rare sugar -allulose as a substitute sweetener is produced through the isomerization of -fructose by -tagatose 3-epimerases (DTEases) or -allulose 3-epimerases (DAEases). -Allulose is a kind of low energy monosaccharide sugar naturally existing in some fruits in very small quantities. -Allulose not only possesses high value as a food ingredient and dietary supplement, but also exhibits a variety of physiological functions serving as improving insulin resistance, antioxidant enhancement, and hypoglycemic controls, and so forth. Thus, -allulose has an important development value as an alternative to high-energy sugars. This review provided a systematic analysis of -allulose characters, application, enzymatic characteristics and molecular modification, engineered strain construction, and processing technologies. The existing problems and its proposed solutions for -allulose production are also discussed. More importantly, a green and recycling process technology for -allulose production is proposed for low waste formation, low energy consumption, and high sugar yield.