Prospective bioconversion of CO2 and CO into fine chemicals via halophilic purple phototrophic bacteria

Abstract

Microbial conversion of cheap and prob- lematic carbon sources, like CO 2 and CO, into fine chemicals offers a promising green alternative to numerous traditionally fossil fuel-based industries such as steel, cement, and pharmaceuticals produc- tion. Purple phototrophic bacteria (PPB) are emerg- ing as versatile key players in carbon–neutral systems due to their anoxygenic photosynthesis and diverse metabolic capabilities, enabling the transformation of carbon and nutrients into a wide range of valua- ble products. Traditionally positioned to treat organic carbon and produce medium-value products like bio- plastics and biomass, PPB also exhibit autotrophic capabilities, enabling the valorization of waste gases, such as CO2 and CO. A key strength of PPB is their metabolic and ecological diversity, including spe- cies inhabiting saline environments. Halophilic bac- teria are known producers of valuable chemicals for pharmaceutical and medical applications, such as osmolytes (ectoine, hydroxyectoine), pigments, amino acids (proline) and natural coenzymes (ubiqui- none), yet halophilic PPB remain underexplored in green upcycling processes. This study identified halophilic PPB capable of transforming waste gases into health and wellness products. Through a compre- hensive literature review, we compiled a list of halo- philic PPB and mined their genomes for genes linked to CO₂/CO utilization as carbon sources. Further genomic search revealed genes encoding enzymes for ectoine/hydroxyectoine, proline, ubiquinone, and carotenoids (lycopene, β-carotene, spirilloxanthin, and spheroidene). We identified 276 genomes of PPB with the genomic potential to valorise CO₂/CO into health-promoting ingredients, highlighting 22 spe- cies capable of producing three or more chemicals simultaneously. These findings highlight the untapped potential of halophilic PPB as bio-platforms for sus- tainable pharmaceutical production.