Recent Advances in the Production and Biosynthesis of Oleanane-Type Pentacyclic Triterpenoids.

Oleanane-type pentacyclic triterpenoids are a class of naturally occurring specialized metabolites with diverse biological activities. Conventional plant extraction and chemical synthesis are constrained by low yields, high costs, and a reliance on natural resources. With the development of synthetic biology and metabolic engineering, the biosynthetic pathways of these compounds can now be systematically reconstructed and optimized, providing new opportunities for efficient production. This review summarizes the classification of oleanane-type pentacyclic triterpenoids and outlines their biosynthetic pathways and recent progress in production platforms such as plant in vitro culture and microbial cell factories. In addition, we discuss major engineering strategies used to improve triterpenoid production, including increasing precursor supply, reducing competing pathways, implementing enzyme engineering and engineering cofactors, improving protein performance, subcellular compartmentalization, enhancing transport, and optimizing fermentation conditions. In view of the current progress, this review also identifies persistent challenges in the biosynthesis of these compounds and outlines potential strategies to address them.