Research progress on biosynthesis and regulation of monoterpenoid compounds

Biosynthesis and Biotransformation of Plant Triterpenoids: Current Advances and Future Perspectives.

Advances in engineering microalgae for heterologous terpenoid synthesis: A review.

Terpenoids are a class of natural products widely distributed in living organisms, with isoprene as their fundamental structural unit. However, traditional plant extraction and chemical synthesis methods are often limited by low product purity, difficult separation, and complex synthetic steps, making it challenging to meet the demands of large-scale production. Conventional hosts such as Escherichia coli and Saccharomyces cerevisiae are utilized for terpenoid synthesis due to their advantages of short growth cycles and controllable cultivation conditions. Nevertheless, the complexity of terpenoid biosynthetic pathways poses significant challenges for these hosts in producing structurally complex terpenoids. In contrast, microalgae as photosynthetic microorganisms, possess well-developed endogenous terpenoid metabolic pathways, abundant precursor pools, and subcellular structures and regulatory mechanisms similar to those of plants, demonstrating significant advantages in the heterologous production of complex terpenoids. This review systematically summarizes recent advances in the production of heterologously synthesized terpenoids in eukaryotic microalgae, ranging from monoterpenes to triterpenes, and provides an in-depth analysis of key engineering strategies, including MEP/MVA pathway regulation, gene expression optimization, subcellular compartmentalization, and cultivation process intensification. In addition, the application potential of advanced tools such as CRISPR/Cas, microalgae-microorganism co-culture, and artificial intelligence is introduced. Finally, the major bottlenecks faced by microalgae as a sustainable green cell factory for terpenoid production are briefly analyzed, and future research directions are proposed.

Chemical Profiling of Monoterpenes and Genome-Wide Discovery of Monoterpene Synthases in Artemisia annua

The Biosynthesis of a Fungal Flavonoid, Chlorflavonin, Precisely Controlled by Two Types of Equilibrium States.

Flavonoids are polyphenolic natural products predominantly isolated from plants and exhibit a diverse array of biological activities. Because they serve as important pharmaceuticals and nutraceuticals, there is a strong demand for their sustainable supply. Chlorflavonin is a rare fungal flavonoid with potent antitubercular activity. While its biosynthetic enzymes are expected to be valuable tools for application in fungal production of flavonoids, the biosynthetic pathway remains unknown. Here, we elucidate the complete biosynthetic pathway for chlorflavonin through detailed functional analysis of each biosynthetic enzyme. Previously, stepwise and straightforward introduction of 3-, 7-, and 8-methoxy; 2'-hydroxy; and 3'-chloro functionalities have been proposed. In contrast to this proposal, we uncovered an intricate biosynthetic route involving a dynamic interconversion between the 6- and 8-methoxy forms of flavonoid skeletons mediated by the chalcone isomerase CfvF and the flavin-dependent oxygenase CfvI. CfvF interconverted the 6- and 8-methoxyflavanones, likely via a chalcone intermediate. CfvI oxidized the chemically inert 2,3-double bond of flavanone, giving the hemiacetal product. Although these enzymes generate products existing in equilibrium states, respective downstream enzymes catalyze selective conversion of one specific species, facilitating smooth progression to the final product. We also solved the crystal structure of CfvK, the dehydratase that selectively converts the 8-methoxy form of the CfvI product. Through analyzing the structure complexed with its substrate and product and site-directed mutagenesis, key residues determining the substrate selectivity were identified. Our comprehensive analysis established a rational framework for preparing 46 flavonoids, including unnatural ones, setting the stage for fungal production of structurally diverse flavonoids.

Terpenoid biosynthesis in yeasts: metabolic diversity and opportunities for food fermentation.

Terpenoids are key contributors to aroma in fermented foods and beverages, yet yeast has traditionally been considered a poor source of de novo monoterpenes. Increasing evidence shows that fermentative yeasts possess an intrinsic capacity to produce volatile isoprenoids through the native mevalonate pathway in the absence of plant precursors. Central to this metabolic plasticity is the prenyltransferase Erg20p, which regulates the balance between geranyl diphosphate (GPP) and farnesyl diphosphate. Variations in ERG20 structure and kinetics can enhance GPP availability, enabling monoterpene formation via metabolic 'leakage', as previously observed for geraniol production. In parallel, several yeast species naturally produce sesquiterpenes such as farnesol and nerolidol. These insights highlight new opportunities to exploit yeast metabolic diversity through non-GMO (Genetic Modified Organisms) strategies for terpene-driven flavor innovation in food fermentations.

Strategic selection of microbial cell factories for sustainable and application-specific terpenoid production

Terpenoids (isoprenoids) constitute one of the largest and most structurally diverse families of natural products with application ranging from flavors, pharmaceuticals to biofuels. Conventional extraction from plants is often limited by low yields, seasonal variability, and environmental constraints; whereas, chemical synthesis requires toxic chemicals and energy-intensive processes. Consequently, microbial cell factories have emerged as sustainable and industrially scalable alternatives for terpenoid biosynthesis. Different microorganisms possess distinct physiological and metabolic advantages, including efficient precursor supply, tolerance to toxic products, internal storage for hydrophobic compounds, utilization of renewable carbon sources, and compatibility with complex biosynthetic pathways. Furthermore, several microbial hosts have strains with Generally Recognized as Safe (GRAS) status, making them attractive candidates for food and nutraceutical applications, although their regulatory acceptance ultimately depends on the production strain, genetic modifications, manufacturing process, product, and intended use. In addition, photosynthetic cyanobacteria offer a promising platform for direct conversion of CO2 into terpenoids, providing opportunities for more resource-efficient and sustainable biomanufacturing. Therefore, strategic host selection is a crucial step in designing efficient microbial platforms for terpenoid production. The present review provides a host-centric perspective by comparing conventional and emerging microbial cell factories, highlighting their physiological strengths, product spectrum, industrial applicability, and strategic considerations for sustainable and application-specific terpenoid biomanufacturing.