Aqueous-rich flow intensification for enzymatic transesterification of rose geranium oil in a coiled flow inverter microreactor
Year: 2026
Type: preprint
Abstract: Enzyme-assisted valorisation of crude floral oils into high-value fragrance esters is constrained by mass-transfer limitations and limited productivity in conventional batch reactors. Rose geranium oil, a naturally complex and terpene-rich multicomponent feedstock containing geraniol, citronellol and numerous other volatile constituents, was selected to investigate continuous enzymatic transesterification directly from a crude floral oil. Using Pseudomonas fluorescens lipase (PFL), geraniol and citronellol were selectively transesterified within the multicomponent oil, without prior isolation of these constituents. A process-intensified strategy was developed using a coiled flow inverter (CFI) microreactor. Aqueous-rich biphasic slug flow at an aqueous-to-organic ratio of 9:1, providing a specific interfacial area of 2319 m 2 m -3 , increased the apparent volumetric mass-transfer coefficient (kLa) by approximately 5-fold for geraniol and 7-fold for citronellol relative to batch operation. At 60 °C and a residence time of 5 min, the CFI achieved 99 % geraniol and 93 % citronellol conversion at 0.2 M rose geranium oil, while maintaining 91 % and 71 % conversion, respectively, at 1.4 M. Increasing the residence time to 7 min increased citronellol conversion at 1.4 M to 95 %. At 1.4 M, the 2 mL CFI provided calculated productivities of approximately 572 g day -1 for geranyl ester and 422 g day -1 for citronellyl ester, assuming continuous operation for 24 h. These results establish aqueous-rich segmented flow as an effective strategy for intensifying selective enzymatic transesterification within a compositionally complex terpene feedstock. The combination of selective conversion, enhanced interphase mass transfer and high calculated productivity provides a basis for the continuous valorisation of rose geranium oil and other complex floral oils into high-value fragrance esters.
Source: ChemRxiv
Institutions: University of Nottingham, The University of Adelaide
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7211967801