Abstract
Human milk oligosaccharides (HMOs) are naturally occurring, non-digestible sugars found in human milk. They have recently become a popular target for industrial synthesis due to their positive effects on the developing gut microbiome and immune system of infants. Microbial synthesis has shown great promise in driving down the cost of these sugars and making them more available for consumers and researchers. The application of common metabolic engineering techniques such as gene knockouts, gene overexpression, and expression of exogenous genes has enabled the rational design of whole-cell biocatalysts which can produce increasingly complex HMOs. Herein, we discuss how these strategies have been applied to produce a variety of sugars from sialylated to complex fucosylated HMOs. With increased availability of HMOs, more research can be done to understand their beneficial effects.