Engineering Escherichia coli for the production of polyketide-based platform chemicals
Master of Science
The current chemical industry produces a diverse array of industrial chemicals from a handful of highly reduced byproducts (termed "platform chemicals") derived from oil refining. However, petroleum is a non-renewable resource, and increases in its cost have created pressure to convert the chemical industry into one that is renewable to ensure its long-term viability. To complete this objective, one approach is the conversion of biomass to platform chemicals through fermentation by Escherichia coli . One such platform chemical is methyl ketone, which can be readily converted to dienes that can directly replace existing platform chemicals such as ethylene. To bestow non-native methyl ketone production capability to E. coli from glucose, the polyketide biosynthesis pathway was exploited in conjunction with grafting in a heterologous methyl ketone synthesis pathway found in wild tomato species Solanum habrochaites to produce the methyl ketones. Cultivation under microaerobic conditions improved titers and yields, and further engineering to knock out the native competitive pathways that become activated under microaerobic conditions led to significantly improved strains. The final strain, ΔadheΔldhaΔptaΔpoxB [pTrcHis2A-shmks2-mks1], produced up to 450 mg/L of methyl ketones at 17 mg of methyl ketones produced per gram of glucose consumed under optimized operating conditions in minimal media supplemented with glucose.
Applied sciences; Pure sciences; Alternative energy; Biochemistry; Chemical engineering