Microbial production of γ-curcumene in metabolically engineered Escherichia coli using a novel γ-curcumene synthase from Parthenium argentatum.

Abstract

BACKGROUND: Terpenoids are attractive targets for sustainable biomanufacturing because of their structural diversity and potential applications in fuels and high-value chemicals. Among sesquiterpenes, γ-curcumene is a promising yet underexplored molecule, and its efficient microbial production has not been established. In this study, we identified a previously uncharacterized γ-curcumene synthase PaCS from Parthenium argentatum and evaluated its use for microbial γ-curcumene production in metabolically engineered Escherichia coli. RESULTS: Sequence analysis revealed that PaCS is phylogenetically distinct from the previously reported γ-curcumene synthase from Pogostemon cablin. When expressed in an E. coli strain carrying a heterologous mevalonate pathway, PaCS predominantly produced γ-curcumene, with only minor formation of (-)-α-bisabolol. Product identity was confirmed by GC-MS and NMR analyses. Biochemical characterization of recombinant PaCS showed maximal activity at 35 °C and pH 8.5, with Mg²⁺ as the preferred divalent metal ion. For microbial production, culture conditions and host background were evaluated, and the evolved strain SBA01 showed the best performance. In fed-batch fermentation, the engineered strain produced up to 1.1 g/L γ-curcumene in terrific broth and 1.03 g/L in modified R medium. In addition, purified γ-curcumene was chemically hydrogenated to bisabolane and dihydro-ar-curcumene, demonstrating its utility as a precursor for fuel-related sesquiterpene hydrocarbons. CONCLUSIONS: This study establishes a microbial production platform for γ-curcumene using a novel γ-curcumene synthase from P. argentatum and metabolically engineered E. coli. The results expand the available terpene synthase toolbox and provide a foundation for the biosynthesis and downstream upgrading of γ-curcumene-derived molecules. These findings support the broader use of synthetic biology and metabolic engineering for the production of non-native sesquiterpenes from renewable carbon sources.

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