Metabolic Engineering of Candida glycerinogenes for Sustainable Production of Geraniol

Geraniol is a class of natural products that are widelyused inthe aroma industry due to their unique aroma. Here, to achieve thesynthesis of geraniol and alleviate the intense competition from theyeast ergosterol pathway, a transcription factor-mediated ergosterolfeedback system was developed in this study to autonomously regulateergosterol metabolism and redirect carbon flux to geraniol synthesis.In addition, the modification of ergosterol-responsive promoters,the optimization of transcription factor expression intensity, andstepwise metabolic engineering resulted in a geraniol titer of 531.7mg L-1. For sustainable production of geraniol,we constructed a xylose assimilation pathway in Candidaglycerinogenes (C. glycerinogenes). Then, the xylose metabolic capacity was ameliorated and the growthof the engineered strain was rescued by activating the pentose phosphate(PP) pathway. Finally, we obtained 1091.6, 862.4, and 921.8 mg L-1 of geraniol in a 5 L bioreactor by using pure glucose,simulated wheat straw hydrolysates, and simulated sugarcane bagassehydrolysates, with yields of 47.5, 57.9, and 59.1 mg g(-1) DCW, respectively. Our study demonstrated that C.glycerinogenes has the potential to produce geraniolfrom lignocellulosic biomass, providing a powerful tool for the sustainablesynthesis of other valuable monoterpenes.

Automated summary

In this study, a transcription factor-mediated ergosterol feedback system was developed to regulate the metabolism of ergosterol and redirect carbon flux to geraniol synthesis. Through stepwise metabolic engineering, a geraniol titer of 531.7 mg L-1 was achieved. Additionally, the xylose assimilation pathway was constructed in Candida glycerinogenes, and the strain's growth was improved by activating the pentose phosphate pathway. This resulted in the production of 1091.6, 862.4, and 921.8 mg L-1 of geraniol from different lignocellulosic biomass sources.