Isopropanol production via the thermophilic bioconversion of sugars and syngas using metabolically engineered Moorella thermoacetica.

Background: Isopropanol (IPA) is a commodity chemical used as a solvent or raw material for polymeric products, such as plastics. Currently, IPA production depends largely on high-CO-emission petrochemical methods that are not sustainable. Therefore, alternative low-CO emission methods are required.

Enhancing acetone production from H and CO using supplemental electron acceptors in an engineered Moorella thermoacetica.

Acetogens grow autotrophically and use hydrogen (H) as the energy source to fix carbon dioxide (CO). This feature can be applied to gas fermentation, contributing to a circular economy. A challenge is the gain of cellular energy from H oxidation, which is substantially low, especially when acetate formation coupled with ATP production is diverted to other chemicals in engineered strains.

Reversible Hydrogenase Activity Confers Flexibility to Balance Intracellular Redox in .

Hydrogen (H) converted to reducing equivalents is used by acetogens to fix and metabolize carbon dioxide (CO) to acetate. The utilization of H enables not only autotrophic growth, but also mixotrophic metabolism in acetogens, enhancing carbon utilization. This feature seems useful, especially when the carbon utilization efficiency of organic carbon sources is lowered by metabolic engineering to produce reduced chemicals, such as ethanol.

Autotrophic growth and ethanol production enabled by diverting acetate flux in the metabolically engineered Moorella thermoacetica.

Gas fermentation is a promising biological process for the conversion of CO or syngas into valuable chemicals. Homoacetogens are microorganisms growing autotrophically using CO and H or CO and metabolizing them to form acetate coupled with energy conservation. The challenge in the metabolic engineering of the homoacetogens is divergence of the acetate formation, whose intermediate is acetyl-CoA, to a targeted chemical with sufficient production of adenosine triphosphate (ATP).

Metabolic engineering of Moorella thermoacetica for thermophilic bioconversion of gaseous substrates to a volatile chemical.

Gas fermentation is one of the promising bioprocesses to convert CO or syngas to important chemicals. Thermophilic gas fermentation of volatile chemicals has the potential for the development of consolidated bioprocesses that can simultaneously separate products during fermentation. This study reports the production of acetone from CO and H, CO, or syngas by introducing the acetone production pathway using acetyl-coenzyme A (Ac-CoA) and acetate produced via the Wood-Ljungdahl pathway in Moorella thermoacetica.