Isopropanol production from biomass-derived sugars by metabolically engineered Escherichia coli

The development of bio-based alternatives for the production of fuels and chemicals has grown significantly in recent years. However, sustainable cost-effective technologies will be required to transition from the current petrochemical production routes. Isopropanol is an attractive bio-derived intermediate that can be used as a substitute of methanol to esterify oils and fats for the production of biodiesel as well as a precursor for the production of propylene-based materials such as polypropylene, acrylonitrile, or propylene oxide. Several species belonging to the Clostridium genus have the capability to reduce acetone to isopropanol. However, these strains also produce butanol as a by-product reducing the isopropanol yield and hindering the separation process. Therefore, heterologous expression of clostridial genes in well-stablished industrial microorganisms has been pursued. In this work, a recombinant Escherichia coli strain harboring an isopropanol synthesis pathway from Clostridium sp. was used to evaluate the production of this secondary alcohol from biomass-derived sugars. Bench-scale batch and fed-batch fermentations are presented, and results are compared in terms of titer, yield, and productivity.