Metabolic Engineering of Candida glycerinogenes for Sustainable Production of Geraniol

Geraniol is a class of natural products that are widely used in the aroma industry due to their unique aroma. Here, to achieve the synthesis of geraniol and alleviate the intense competition from the yeast ergosterol pathway, a transcription factor-mediated ergosterol feedback system was developed in this study to autonomously regulate ergosterol metabolism and redirect carbon flux to geraniol synthesis. In addition, the modification of ergosterol-responsive promoters, the optimization of transcription factor expression intensity, and stepwise metabolic engineering resulted in a geraniol titer of 531.7 mg L^-1. For sustainable production of geraniol, we constructed a xylose assimilation pathway in Candida glycerinogenes (C. glycerinogenes). Then, the xylose metabolic capacity was ameliorated and the growth of 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 bagasse hydrolysates, 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 geraniol from lignocellulosic biomass, providing a powerful tool for the sustainable synthesis of other valuable monoterpenes.