Whole-Cell Production of Patchouli Oil Sesquiterpenes in Escherichia coli: Metabolic Engineering and Fermentation Optimization in Solid–Liquid Phase Partitioning Cultivation

Abstract

Patchouli oil is a major ingredient in perfumery, granting a dark-woody scent due to its main constituent (−)-patchoulol. The growing demand for patchouli oil has raised interest in the development of a biotechnological process to assure a reliable supply. Herein, we report the production of patchouli oil sesquiterpenes by metabolically engineered Escherichia coli strains, using solid–liquid phase partitioning cultivation. The (−)-patchoulol production was possible using the endogenous methylerythritol phosphate pathway and overexpressing a (−)-patchoulol synthase isoform from Pogostemon cablin but at low titers. To improve the (−)-patchoulol production, the exogenous mevalonate pathway was overexpressed in the multi-plasmid PTS + Mev strain, which increased the (−)-patchoulol titer 5-fold. Fermentation was improved further by evaluating several defined media, and optimizing the pH and temperature of culture broth, enhancing the (−)-patchoulol titer 3-fold. To augment the (−)-patchoulol recovery from fermentation, the solid–liquid phase partitioning cultivation was analyzed by screening polymeric adsorbers, where the Diaion HP20 adsorber demonstrated the highest (−)-patchoulol recovery from all tests. Fermentation was scaled-up to fed-batch bioreactors, reaching a (−)-patchoulol titer of 40.2 mg L–1 and productivity of 20.1 mg L–1 d–1. The terpene profile and aroma produced from the PTS + Mev strain were similar to the patchouli oil, comprising (−)-patchoulol as the main product, and α-bulnesene, trans-β-caryophyllene, β-patchoulene, and guaia-5,11-diene as side products. This investigation represents the first study of (−)-patchoulol production in E. coli by solid–liquid phase partitioning cultivation, which provides new insights for the development of sustainable bioprocesses for the microbial production of fragrant terpenes.