Production of geraniol by a solvent-tolerant Serratia marcescens without the formation of geraniol derivatives

Abstract

Geraniol is an acyclic monoterpene compound with a distinct rose-like fragrance, extensively used in fragrances, cosmetics, pesticides, and pharmaceuticals. The traditional extraction of geraniol from plants is limited by the supply of raw materials, which is insufficient to meet market demands. The solvent-tolerant Serratia marcescens demonstrates a high potential for geraniol production, so it was selected as a host for the production of geraniol. We constructed a geraniol biosynthetic pathway in S. marcescens HBQA7 by integrating seven enzymes with high expression activity, successfully achieving the production of geraniol. To enhance the biosynthesis of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), we engineered the downstream pathway of the mevalonate (MVA) pathway by rearranging the order of phosphomevalonate kinase (PMK), phosphomevalonate decarboxylase (PMD), and isopentenyl diphosphate isomerase (IDI). Furthermore, an optimal geraniol synthase (ObGES) from Ocimum basilicum was determined for geraniol biosynthesis by evaluating five different geraniol synthases (GES). To further increase the production of geranyl pyrophosphate (GPP), we compared different geranyl diphosphate synthase (GPPS) and found that the enzyme derived from Abies grandis (AgGPPS) was the most effective. Based on these findings, we optimized the linker sequences for fusion expression, thereby improving geraniol production efficiency. Ultimately, the geraniol titer reached 947.6 mg/L in shake flask fermentation. Upon scaling up the process, the geraniol production further increased to 2976.2 mg/L in 5 L bioreactor. This represents the highest yield of geraniol to date in S. marcescens. This research provides a theoretical foundation for the production of other terpenoid compounds in S. marcescens.