Advanced Butanol and Hexanol Production from CO2: Integrating Genetically Modified Clostridium strains in Bioelectrochemical Systems

The production of butanol and hexanol from syngas (CO and CO2) fermentation represents a significant advancement in sustainable chemical manufacturing.

This project aims to enhance the efficiency of this process by leveraging the capabilities of Clostridium ljungdahlii, a bacterium known for its robust syngas fermentation capabilities.

C. ljungdahlii can convert CO2 into valuable products like butanol and hexanol, but current production levels are limited. Existing research shows that engineered strains of Clostridium can produce butanol at levels of 6–8 g/L from syngas.

With ongoing advancements in genetic engineering, these yields are expected to rise to 10 g/L, and potentially up to 20 g/L with further metabolic engineering and optimized fermentation conditions.

Similarly, while current hexanol production stands at 1–2 g/L, genetic engineering holds the potential to increase this to 2–3 g/L by enhancing chain elongation and managing acetate accumulation.The project here focuses on two main objectives: a) optimizing genetic modifications in Clostridium strains and integrating bioelectrochemical systems (BES) to address the current limitations.

Genetic engineering efforts will target the Wood-Ljungdahl pathway (WLP), a crucial metabolic route for converting CO2 and CO into acetate.

By knocking out the acoA gene (acetyl-CoA synthetase) and upregulating adhE (alcohol dehydrogenase), we aim to redirect carbon flux from acetate production to alcohol synthesis.

Additionally, utilizing BES will help mitigate acetate toxicity and enhance product yields through electrochemical stimulation, which improves cellular redox metabolism and supports the conversion of excess acetate into butanol (C4) and hexanol (C6).

In effect, this combined approach will increase the production of multi-carbon chemicals in the system, which will provide new insights and improved efficiency in BES for increased CO2 fixation and bioconversion.