Review in Structure–Activity Relationships, Synthetic Regulation, and Applications of Mono/Di-Rhamnolipids

Rhamnolipids (RLs) are natural biosurfactants produced by microbial fermentation. They exhibit excellent surface activity, environmental compatibility, and versatile biological activities, with broad application potential in energy development, environmental remediation, personal care, and biomedicine. In recent years, RLs have garnered significant attention due to the structural divergence between mono-rhamnolipids (mono-RLs) and di-rhamnolipids (di-RLs). Their distinct physicochemical and biological properties necessitate structure-function-guided "tailor-made" synthesis. Notably, the compositional fluctuation of naturally occurring RL mixtures constrains their high-value utilization. This review systematically summarizes the structure-function relationships, microbial biosynthetic pathways, and regulatory approaches of mono-RLs and di-RLs, with a core focus on the targeted production of RLs with specific mono-/di-RL ratios. The review also highlights the application-specific suitability of the two RL congeners. It aims to provide a theoretical foundation and technical reference for the precision manufacturing and commercialization of RLs in energy, environment, health, and other related fields.