D-allulose 3-epimerase for low-calorie D-allulose synthesis: microbial production, characterization, and applications

Abstract

D-allulose, an epimer of D-fructose at C-3 position, is a low-calorie rare sugar with favorable physiochemical properties and special physiological functions, which displays promising perspectives in the food and pharmaceutical industries. Currently, D-allulose is extremely sparse in nature and is predominantly biosynthesized through the isomerization of D-fructose by D-allulose 3-epimerase (DAEase). In recent years, D-allulose 3-epimerase as the key biocatalyst for D-allulose production has received increasing interest. The current review begins by providing a summary of D-allulose regarding its characteristics and applications, as well as different synthesis pathways dominated by biotransformation. Then, the research advances of D-allulose 3-epimerase are systematically reviewed, focusing on heterologous expression and biochemical characterization, crystal structure and molecular modification, and application in D-allulose production. Concerning the constraint of low yield of DAEase for industrial application, this review addresses the various attempts made to promote the production of DAEase in different expression systems. Also, various strategies have been adopted to improve its thermotolerance and catalytic activity, which is mainly based on the structure-function relationship of DAEase. The application of DAEase in D-allulose biosynthesis from D-fructose or low-cost feedstocks through single- or multi-enzymatic cascade reaction has been discussed. Finally, the prospects for related research of D-allulose 3-epimerase are also proposed, facilitating the industrialization of DAEase and more efficient and economical bioproduction of D-allulose.

Keywords:

• D-allulose
• D-allulose 3-epimerase
• biotransformation
• heterologous expression
• biochemical characterization
• molecular modification

Disclosure statement

The authors declare no competing interests.

Additional information

Funding

This work was financially supported by the National Key R&D Program of China (2022YFF1100600/2022YFF1100602), the National Natural Science Foundation of China (32272263), the Science and Technology Support Program (Modern Agriculture) of Jiangsu Province (BE2022323), and an industry project from Guangzhou Welbon Biological Technology Co., Ltd (A-0008525-00-00). Some of the icons in Figures 1, 2 and 5 are designed by Freepik (https://www.freepik.com/).