Heterologous Production of Isopropanol Using Metabolically Engineered Strains.

The depletion of fossil fuel resources and the CO emissions coupled with petroleum-based industrial processes present a relevant issue for the whole of society. An alternative to the fossil-based production of chemicals is microbial fermentation using acetogens. Acetogenic bacteria are able to metabolize CO or CO (+H) via the Wood-Ljungdahl pathway. As isopropanol is widely used in a variety of industrial branches, it is advantageous to find a fossil-independent production process. In this study, was employed to produce isopropanol via plasmid-based expression of the enzymes thiolase A, CoA-transferase, acetoacetate decarboxylase and secondary alcohol dehydrogenase. An examination of the enzymes originating from different organisms led to a maximum isopropanol production of 5.64 ± 1.08 mM using CO + H as the carbon and energy source. To this end, the genes (encoding thiolase A) and (encoding CoA-transferase) of , (encoding acetoacetate decarboxylase) originating from and (encoding secondary alcohol dehydrogenase) of DSM 6423 were employed. Since bottlenecks in the isopropanol production pathway are known, optimization of the strain was investigated, resulting in a 2.5-fold increase in isopropanol concentration.