The use of isomerases and epimerases for the production of the functional sugars mannose, allulose and tagatose from Fructose.

Fructose, a common monosaccharide in nature extensively utilized in the food industry, poses a risk of elevated chronic disease incidence with excessive consumption. The global movement for a healthier living has sparked a quest for sugar reduction in foodstuff. The growing concern regarding the adverse impact of excessive sugar consumption on public health has led to significant interest in investigating healthier sugar alternatives. Research efforts have refocused on converting fructose into high-value, reduced-calorie functional sugars. Fructose can undergo direct conversion into three such sugars-mannose, allulose, and tagatose-via a streamlined bioconversion process. Allulose and tagatose, epimers of fructose, are derivable directly from fructose through C-3 and C-4 epimerization processes, whereas mannose, the aldose isomer of fructose, can be synthesized via isomerization pathways. This article aims to present recent advancements in the physiological functions, production methods, and applications of functional sugars derived from fructose. Particularly, it focuses on the bioproduction of mannose, allulose, and tagatose from fructose, encompassing discussions on the recent progress in the related isomerases and epimerases, such as mannose isomerase/lyxose isomerase, ketose 3-epimerase, and tagatose 4-epimerase. This review will provide a fresh perspective on the high-value biological utilization of fructose resources.