Biosynthesis of Galactooligosaccharides: Enzymatic Strategies, Physiological Functions, and Applications

In recent years, nutrition and health have become topics of widespread societal concern, and galactooligosaccharides (GOS) have garnered significant interest as prebiotics. Composed of one to nine galactose units terminated by a glucose molecule, GOS exhibit remarkable thermostability, high water solubility, strong humectancy, and low caloric value. They provide various physiological benefits, including prebiotic activity, gut health maintenance, antibacterial, antiadhesive, and anti-inflammatory effects, as well as systemic regulation of blood sugar, lipids, immune homeostasis, and metabolic diseases. These properties support broad applications in the food industry, breeding field, material science, and medical science. Enzymatic production using β-galactosidases is the primary industrial method for GOS synthesis. This review provides an overview of recent advances in β-galactosidase biochemistry, crystal structures, catalytic mechanisms, molecular modification, immobilization, and heterologous expression, along with GOS physiological functions, production, applications, and whey utilization. Future opportunities for GOS research and development are also briefly discussed.