Comparative reaction engineering analysis of different acetogenic bacteria for gas fermentation

Area of Science:

• Microbial biotechnology
• Industrial microbiology
• Biochemical engineering

Background:

• Syngas fermentation presents a sustainable alternative to traditional chemical production methods.
• Autotrophic acetogens, particularly less-studied species, require thorough characterization for optimizing chemical synthesis.
• Acetobacterium woodii serves as a benchmark for evaluating the performance of other acetogenic bacteria.

Purpose of the Study:

• To characterize the autotrophic process performance of several understudied acetogenic bacteria.
• To compare the growth rates, biomass concentrations, and product formation of these acetogens.
• To identify promising strains for the production of chemicals from syngas.

Main Methods:

• Standardized batch fermentation experiments were conducted in controlled stirred-tank bioreactors.
• Continuous supply of gaseous substrates, carbon dioxide (CO2) and hydrogen (H2), was provided.
• Growth kinetics and product yields (acetate, formate, ethanol, butyrate) were quantitatively analyzed.

Main Results:

• Sporomusa ovata and Acetobacterium wieringae exhibited the highest growth rates and biomass yields.
• S. ovata achieved the highest volumetric (17.96 g L⁻¹ d⁻¹) and specific acetate formation rates (21.03 g g⁻¹ d⁻¹), reaching a final concentration of 32.2 g L⁻¹.
• Formate accumulation was observed across all tested acetogens, while ethanol and butyrate were produced by specific strains.

Conclusions:

• Sporomusa ovata displays exceptional process performance, making it a strong candidate for syngas fermentation.
• The strain's high acetate production capacity suggests its potential as a host for producing valuable chemicals via metabolic engineering.
• Further research utilizing synthetic biology tools could unlock S. ovata's capability for synthesizing non-natural compounds from syngas.