Advances in the Biosynthesis of D-Tagatose: From Metabolism, Physiological Activities, Key Enzyme Catalysis to Multi-Substrate Conversion Strategies.

D-tagatose is a rare sugar found in nature that contains less than one-third of sucrose's calories while maintaining 92% of its sweetness. Owing to its physiological properties, such as lowering blood sugar, preventing obesity, anti-caries, and regulation of intestinal flora, it is being used as a new kind of healthy sweetener. This paper conducts a systematic review of advances in its biosynthesis research, focusing on the catalytic mechanisms of key enzymes and the multi-substrate conversion strategies. Specifically, by analyzing L-Arabinose Isomerase (L-AI), the study compares enzymatic conversion pathways for various substrates, including monosaccharides (D-galactose, D-fructose, D-glucose, etc.), disaccharides (lactose, sucrose), and maltodextrin. This study thoroughly examines the advantages and limitations of each pathway in terms of reaction efficiency, substrate cost, and industrial adaptability. The goal of this research is to provide guidance for D-tagatose's industrial manufacturing, advancing its efficient biosynthesis and commercial application.