## 4 Conclusions  
We engineered the yeast _S. cerevisiae_ to produce fragrant terpenids in sandalwood and agarwood. Specifically, we constructed strain FPPY005_39850, which overexpresses all eight genes in the mevalonate pathway under the galactose-inducible system. Using this engineered strain as the background strain, we screened seven distinct terpene synthasegenes from agarwood, sandalwood, and related plant species using a plasmid-based expression system. Five terpene synthases, namely _As_SeTSPS1, _Ac_HS1, _C_ITPS2, _Amd_GS1, and _Z_z_BES2, led to the production of fragrant terpenoids, including \(\alpha\)-humulene, \(\delta\)-guaiene, \(\alpha\)-santalene, and \(\beta\)-eudesmol in yeast. We further improved the production titer of the terpenoids by repressing the expression of _ERG_9, a key enzyme from a competing pathway, as well as employing enzyme fusion of the FPPS and the corresponding terpene synthase to bring the enzymes into proximity. Our final engineered strains produced fragrant terpenoids at a titer of up to 101.7 \(\pm\) 6.9 mg/L (in the case of \(\alpha\)-humulene). Moreover, to our knowledge, this is the first demonstration of \(\beta\)-eudesmol production in a yeast system. We envision our work will pave the way for a scalable route to these fragrant terpenoids and further establish _S. cerevisiae_ as a versatile production platform for fuels and high-value chemicals. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/fermentation8090429/s1](https://www.mdpi.com/article/10.3390/fermentation8090429/s1)]([https://www.mdpi.com/article/10.3390/fermentation8090429/s1](https://www.mdpi.com/article/10.3390/fermentation8090429/s1)), Detailed description of plasmid and strain construction; Table S1: Primers used in this study; Figure S1: Total ion chromatograms and mass spectra obtained from engineered yeast strain producing \(\delta\)-guaiene; Figure S2: Total ion chromatograms and mass spectra obtained from engineered yeast strain producing \(\alpha\)-santalene; Figure S3: GC-FID chromatograms of engineered yeast strain producing \(\beta\)-eudesmol; Figure S4: Mass spectra of the dodecane sample containing \(\beta\)-eudesmol from engineered yeast strain producing \(\beta\)-eudesmol; Figure S5: AlphaFold-predicted structures of the ACHS1 and FPPS as standalone enzymes; Figure S6: AlphaFold-predicted structure of the FPPS-GGGS-AcHS1 enzyme fusion; Figure S7: AlphaFold-predicted structure of the FPPS-GGGGS-AcHS1 enzyme fusion; Figure S8: AlphaFold-predicted structures of the AmdGS1 and FPPS as standalone enzymes; Figure S9: AlphaFold-predicted structure of the FPPS-GSG-AmdGS1 enzyme fusion; Figure S10: AlphaFold-predicted structure of the FPPS-GGGS-AmdGS1 enzyme fusion; Figure S11: AlphaFold-predicted structures of the CITPS2 and FPPS as standalone enzymes; Figure S12: AlphaFold-predicted structure of the FPPS-GGGS-CITPS2 enzyme fusion; Figure S13: AlphaFold-predicted structure of the FPPS-GGGGS-CITPS2 enzyme fusion; Figure S14: AlphaFold-predicted structures of the ZzBES2 and FPPS as standalone enzymes; Figure S15: AlphaFold-predicted structure of the FPPS-GGGS-ZzBES2 enzyme fusion; Figure S16: AlphaFold-predicted structure of the FPPS-GGGGS-ZzBES2 enzyme fusion. File S1: A detailed description of plasmid and strain construction. Conceptualization, W.R.; methodology, P.P., W.S., T.P. and W.R.; validation, P.P. and W.S. ; formal analysis, P.P. and W.R.; investigation, P.P. and W.R.; resources, W.R.; data curation, P.P. and W.R.; writing--original draft preparation, W.R. and P.P. ; writing--review and editing, W.R.; visualization, W.R.; supervision, W.R.; project administration, W.R. and S.T. ; funding acquisition, W.R. All authors have read and agreed to the published version of the manuscript. The project was funded by the Biochemical and Biofuels (2B) project, \"Development of an efficient yeast system for the production of high-value terpenoids\", supported by the National Science and Technology Development Agency (grant number P-19-52252). Not applicable.