Synthesis of N-Acetyllactosamine and N-Acetyllactosamine-Based Bioactives

N-Acetyllactosamine (LacNAc) or more specifically β-d-galactopyranosyl-1,4-N-acetyl-d-glucosamine is a unique acyl-amino sugar and a key structura lunit in human milk oligosaccharides, an antigen component of many glycoproteins, and an antiviral active component for the development of effective drugs against viruses. LacNAc is useful itself and as a basic building block for producing various bioactive oligosaccharides, notably because this synthesis may be used to add value to dairy lactose. Despite a significant amount of information in the literature on the benefits, structures, and types of different LacNAc-derived oligosaccharides, knowledge about their effective synthesis for large-scale productionis still in its infancy. This work provides a comprehensive analysis of existing production strategies for LacNAc and important LacNAc-based structures, including sialylated LacNAc as well as poly- and oligo-LacNAc. We conclude that direct extraction from milk is too complex, while chemical synthesis is also impractical at an industrial scale. Microbialroutes have application when multiple step reactions are needed, but the major route to large-scale biochemical production will likely lie with enzymatic routes, particularly those using β-galactosidases (for LacNAc synthesis), sialidases (for sialylated LacNAc synthesis), and β-N-acetylhexosaminidases (for oligo-LacNAcsynthesis). Glycosyltransferases, especially for the biosynthesis of extended complex LacNAc structures, could also play a major role in the future. In these cases, immobilization of the enzyme can increasestability and reduce cost. Processing parameters, such as substrate concentration and purity, acceptor/donor ratio, water activity, and temperature, can affect product selectivity and yield. More work isneeded to optimize these reaction parameters and in the development of robust, thermally stable enzymes to facilitate commercial production of these important bioactive substances.