Acetogens: Biochemistry, Bioenergetics, Genetics, and Biotechnological Potential

The review discusses the present-day data on the biochemistry, bioenergetics, and genetics of acetogens, as well as their biotechnological potential. Acetogens are anaerobic gram-positive bacteria capable of growth on gaseous substrates: CO2, CO, H2. These bacteria have a characteristic biochemical pathway of CO2 reduction to acetyl-CoA, termed the reductive acetyl-CoA pathway or the Wood‒Ljungdahl pathway. This is the only pathway of CO2 fixation coupled to energy storage. Due to their efficient non-photosynthetic CO2 fixation, acetogens may be used for production of chemicals and biofuel in the expected economy based on renewable energy and resources. The shortcomings of acetogens growing on gaseous substrates are low energy provision and a narrow spectrum of terminal metabolites, primarily acetic acid and ethanol with low amounts of butanol and butyric acid. Acetogens are capable of heterotrophic growth on such substrates as sugars, lactate, or alcohols. Mixotrophy, i.e., simultaneous utilization of different substrates by acetogens, is a promising approach to increasing the energy provision. Application of the methods of metabolic engineering is required both for successful coupling of different metabolic pathways and for broadening the range of synthesized products. Genetic tools for the transformation of genomes of acetogens have been considerably improved in recent years.