Engineering Escherichia coli for effective and economic production of cis-abienol by optimizing isopentenol utilization pathway

Abstract

Efficient and economical supply of cis-abienol has attracted extensive attention due to its use as a precursor in the synthesis of ambrox (a cardinal odor of rare ambergris). Increasing awareness in environmental issues and advantages of microbial production–sustainable and green manufacture, have motivated efforts to advance the cis-abienol biosynthesis in more affordable ways. Herein, Escherichia coli cells were employed to scale up cis-abienol production via expressing the concise isopentenol utilization pathway (IUP). Alcohol kinases and isopentenyl phosphate kinases (IPKs) were screened and coordinated to increase dimethylallyl diphosphate (DMAPP) supply, which resulted in approximately 37-fold improvements in the cis-abienol yield, compared with the titer obtained by endogenous MEP pathway. Next, we constructed a double-phosphatase-deficient strain (BD203), resulting in a 40% increase in the cis-abienol titer relative to wild-type strains. By optimization of addition strategies, a cis-abienol titer of 311.8 ± 1.0 mg/L was obtained in strain BD203, which is the highest cis-abienol titer reported in shake flasks and 14.7% of the maximum theoretical yield. Finally, further optimization of the fed-batch fermentation process enabled a cis-abienol titer of 1375.7 mg/L in a 1.3 L bioreactor. Overall, BD203 achieved a substantial increase in the cis-abienol titer in this study and engineering microbes were expected to facilitate progress toward industrial production.