## 4 Discussion
_capsulatus_ under phototrophic and non-phototrophic conditions. For this purpose, the intrinsic iso-prepoid biosynthesis pathway was optimized in terms of its precursor supply. In particular, the P\({}_{nif}\)-based co-expression of _ispA_ and the genetically integrated MVA pathway resulted in a substantial increase in sesquiterpenoid production of around 300%. These results are in agreement with previous studies, where engineering of isoprenoid precursor supply was a valuable tool to increase the terpenoid production in _Rhodobacter_[38; 40; 48] and other bacterial hosts [23; 117; 118; 119; 120; 121; 122; 123; 124; 125]. Also, we were able to increase the terpene production level further by changing the cultivation conditions from bulb light in a 14 mL humage tube to IR light in a 4.5 mL screw neck vial, achieving a final \(\beta\)-caryophyllene titer of 139.29 \(\pm\) 31.35 mg L\({}^{-1}\) and a specific productivity of 1.30 \(\pm\) 0.32 mg g\({}^{-1}\) dry cells h\({}^{-1}\). In recent studies, production titers around 220 mg L\({}^{-1}\)[126] and specific productivities of 1.15 mg g\({}^{-1}\) dry cells h\({}^{-1}\)[127] were achieved in _E. coli_. Thus, we attained yields comparable to the current literature and successfully established _R. capsulatus_ as a heterologous host for the production of \(\beta\)-caryophyllene. Furthermore, the \(\beta\)-caryophyllene yields achieved in _R. capsulatus_ could be sufficient to use this host as a microbial system for in situ agent delivery. In the future, sesquiterpenoid producing _R. capsulatus_ might thus be applicable as cell extracts with biocontrol activities for plant protection or as engineered antibytopathogenic PGP that can be added as live cultures to soils contained in vertical farming. **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/2076-2](https://www.mdpi.com/2076-2)]([https://www.mdpi.com/2076-2](https://www.mdpi.com/2076-2)) 607/9/1/168/s1. Figure S1: Transfer efficiency of the \(\beta\)-caryophyllene reference compound from cultivation medium into the \(n\)-dodecane phase in the presence of intact _R. capsulatus_ cells in humage and screw neck vials, Figure S2: Transfer efficiency of the \(\beta\)-caryophyllene reference compound from cultivation medium into the \(n\)-dodecane phase in the presence of intact and disrupted _R. capsulatus_ cells, Figure S3: Extraction efficiency of the \(\beta\)-caryophyllene reference compound from cultivation medium in the presence of disrupted and intact _R. capsulatus_ cells by repeatedly using \(n\)-dodecane as organic solvent over four days, Figure S4: Comparison of relative \(\beta\)-caryophyllene formation in _R. capsulatus_ production strains cultivated with and without an \(n\)-dodecane layer, Figure S5: Quantification of extracted \(\beta\)-caryophyllene via a calibration curve of \(\beta\)-caryophyllene reference signals in GC-FID analyses, Figure S6: Emission range of different light sources and the absorption spectrum of phototrophically cultivated _R. capsulatus_ cells [128], Figure S7: Effect of \(\beta\)-caryophyllene and \(\beta\)-caryophyllene oxide on the hyphal growth of plant pathogenic fungi, Table S1: Bacterial strains and plasmids used in this study, Table S2: Cultivation vessel specifications, Table S3: Productivities of \(\beta\)-caryophyllene in _R. capsulatus_ SB1003 cultures. **Author Contributions:** Conceptualization, T.D., A.L., K.-E.J., A.S.S.S., F.M.W.G. ; methodology, F.H., Y.S.A., J.H.-H., A.H., S.S.H. ; validation, F.H., S.S.H. ; formal analysis, S.S.H., F.H. ; investigation, F.H., S.S.H., Y.S.A., S.N., O.K. ; writing--original draft preparation, F.H., S.S.H. ; writing--review and editing, T.D., A.S.S.S., A.L., K.-E.J., F.M.W.G. ; visualization, F.H. ; supervision, T.D., A.L., A.S.S.S., project administration, A.L., T.D., A.S.S.S., K.-E.J., F.M.W.G. ; funding acquisition, A.L., T.D., A.S.S., K.-E.J., F.M.W.G. All authors have read and agreed to the published version of the manuscript.