Aerobic syngas conversion: opportunities, challenges, and solutions

Some aerobic bacteria can convert syngas, an energy-dense mixture of CO, H 2 , and CO 2 derived from waste gasification, into platform chemicals and products such as single-cell protein and bioplastics. Despite the enormous theoretical energy yield of aerobic syngas conversion, few cultured bacteria can mediate this process, and none do so quickly or efficiently. This reflects the dual challenges that known pathways of aerobic CO conversion are highly inefficient, and most H 2 -oxidising enzymes are highly CO-sensitive. Here, we propose three strategies to overcome these challenges: evolving and engineering existing syngas-converting strains, isolating novel syngas-converting microbes from gas-rich environments, and introducing CO-insensitive hydrogenases and direct CO conversion pathways into industrial chassis strains. If this can be achieved, efficient aerobic syngas conversion would become a cornerstone of a sustainable bioeconomy. • Aerobic microbial conversion of syngas is an ideal strategy for waste valorisation. • Aerobic syngas conversion is slow due to sensitive H 2 and inefficient CO metabolism. • Combined enzyme, strain, and process engineering are needed to overcome bottlenecks. • Engineered C. necator shows aerobic CO mixotrophy and increased biomass yields. • Isolation from CO/H 2 -rich sites could expand hosts and syngas conversion pathways.