How can alcohol production be improved in carboxydotrophic clostridia?

• Carboxydotrophic clostridia can produce alcohols from syngas and CO-rich gas.
• pH is the key factor governing the shift to solventogenesis in acetogenic bacteria.
• Selection of the adequate medium composition can enhance alcohol production.
• Genetic engineering has the potential to improve strain productivity and resistance.

Clostridia are well-known organisms within the scientific community, and many aspects of their life cycle have been studied. Autotrophic strains are especially interesting as microbial cell factories for industrial purposes. Carboxydotrophic clostridia can use CO2/H2 and/or CO as their only carbon and reducing power sources, and they produce alcohols and acids. Both products can be used as either biofuels or feedstock chemicals for many industrial processes, confirming the control of carboxydotrophic clostridia metabolism as one of the most profitable scientific ambitions to be explored. Here, we review the current state of research on alcohol production by carboxydotrophic clostridia, including a comprehensive overview of their metabolic pathways and the key experimental variables that govern alcohol production. Additionally, the genetic and genomic tools for selective and enhanced solvent production, which are currently under intense development, are discussed. In this context, this review covers the main genetic engineering methods that have been utilized to improve the capabilities of solventogenic carboxydotrophic bacteria.