Systematic Engineering To Enhance Citronellol Production in Yeast

Citronellol is a typical acyclic monoterpene alcohol widely used for fragrance and seasoning in the food industry and as a fungicide of plant origin in agriculture. Microbial cell factories offer a promising green and sustainable approach to efficient citronellol production. Inadequate supply of precursor geranyl pyrophosphate and cofactor NADPH, and monoterpene cytotoxicity are considered major bottlenecks in citronellol production. Additional copies of the mevalonate pathway (ERG10, ERG13, ERG12, ERG19) and peroxisome-localized (ERG8, ERG20^ww, tCrGES, CrIS) genes were integrated for citronellol biosynthesis based on our former citronellol overproduction strain, resulting in a 1.5-fold increase in citronellol production. Moreover, overexpression of nonoxidative pathway genes (TAL1 and TKL1) of the pentose phosphate pathway promotes the NADPH supply, resulting in a 16% increase in citronellol yield. Screening of endogenous transporter proteins and integration of PDR1 increased citronellol production to 3.38 g/L. Ultimately, 10.556 g/L citronellol was attained in Saccharomyces cerevisiae via 100 L of fed-batch fermentation, which is the highest titer in yeast so far. In summary, the titer of citronellol was systematically increased through modification of chassis cells, and the findings provide guidance for the biosynthesis of other monoterpenes.