Adaptive laboratory evolution for improving acetogen gas fermentation

Gas fermentation using acetogens can help humankind transition from petroleum-based industries to more sustainable alternatives. Acetogens are a unique set of organisms that efficiently convert carbon oxide waste gases into chemicals, such as ethanol and acetate. While acetogens are already used in commercially operated bioprocess facilities, the field is still affected by challenging genetic manipulation workflows and a developing knowledge of acetogen metabolism. Adaptive laboratory evolution (ALE) can uniquely contribute here, through evolution of organisms guided by synthetically created niches, which delivers strains with industrially relevant phenotypes and helps to resolve genotype-phenotype relationships. Here, we review the expanding use of ALE for acetogens, showcasing results regarding fundamental understanding of acetogens and improvement of phenotypes - faster growth/substrate utilisation, elimination of media components, improving stress tolerance, and improving growth and robustness in bioreactor cultures. These works provide the field with opportunities to further engineer and manipulate acetogen traits for industrial bioprocesses and improve the understanding of genotype-phenotype relationships.