Advances and Prospects of d-Tagatose Production Based on a Biocatalytic Isomerization Pathway

Abstract

d-tagatose is a low-calorie alternative to sucrose natural monosaccharide that is nearly as sweet. As a ketohexose, d-tagatose has disease-relieving and health-promoting properties. Due to its scarcity in nature, d-tagatose is mainly produced through chemical and biological methods. Compared to traditional chemical methods, biological methods use whole cells and isolated enzymes as catalysts under mild reaction conditions with few by-products and no pollution. Nowadays, biological methods have become a very important topic in related fields due to their high efficiency and environmental friendliness. This paper introduces the functions and applications of d-tagatose and systematically reviews its production, especially by l-arabinose isomerase (L-AI), using biological methods. The molecular structures and catalytic mechanisms of L-AIs are also analyzed. In addition, the properties of L-AIs from different microbial sources are summarized. Finally, we overview strategies to improve the efficiency of d-tagatose production by engineering L-AIs and provide prospects for the future bioproduction of d-tagatose.