Development of Pantoea species As a Platform for the Production of High Value Terpenoids

Plant derived terpenoids represent a diverse class of chemicals with important roles as fragrance and flavour molecules (eg camphor, menthol and citral), dyes and colurants (eg astaxanthin)  as well as high value medicinal compounds such as the antimalarial Artemisinin and the anti-cancer drug Paclitaxel (Taxol).

High volume production of these products can be difficult due reliance on plant production or economic difficulties in synthetic production. These high value terpenoids represent an interesting challenge to metabolic engineering and synthetic biology, not only in being able to produce these chemicals at scale, but also developing novel products via the intermediates of these pathways.

Research into methods of microbial production of Taxol and its derivatives have focused on the precursor pathways leading to geranylgeranyl diphosphate (GGPP), as these are the last non-dedicated steps. This method works well however the p450 mediated hydroxylation steps appear to have limited success in E. coli.

 Instead of optimising the precursor pathways, we have attempted to utilise natural diversity in search of a better host for production of these high value terpenoids, by selecting an organism that already produces a large amount of GGPP and can potentially better mediate p450 hydroxylation reactions.

GGPP can also be converted into carotenoid pigments such as lycopene, β-carotene and canthaxanthin, therefore Carotenoids production can be used as a surrogate measure for predicting how well a species might perform for production of heterologous isoprenoids.   Genes for carotenoid biosynthesis from Pantoea species have been used in many heterologous expression experiments but the organism itself has not been considered as a chassis. As a relatively close phylogenetic relation to E.coli, these Gram negative bacteria are easily transformable, genetically tractable and many tools developed for E. coli function in Pantoea.

We will present details of the progress made and pitfalls encountered during the engineering of wild type Pantoea to produce intermediates of Taxol.