Microbial conversion of carbon dioxide and hydrogen into the fine chemicals hydroxyectoine and ectoine

This study explores a novel conversion of CO₂ into the chemicals hydroxyectoine and ectoine, which are compounds with high retail values in the pharmaceutical industry. Firstly, 11 species of microbes able to use CO₂ and H₂ and that have the genes for ectoines synthesis (ectABCD) were identified through literature search and genomic mining. Laboratory tests were then conducted to ascertain the capacity of these microbes to produce ectoines from CO₂. Results showed that the most promising bacteria for CO₂ to ectoines bioconversion areHydrogenovibrio marinus, Rhodococcus opacus, and Hydrogenibacillus schlegelii.Upon salinity and H₂/CO₂/O₂ ratio optimization,H. marinus accumulated 85 mg of ectoine g biomass^-1. Interestingly, R.opacusand H. schlegelii mainly produced hydroxyectoine (53 and 62 mg g biomass^-1), which has a higher commercial value. Overall, these results constitute the first proof of a novel valorization platform of CO₂ and lay the foundation for a new economic niche aimed at CO₂ recircularization into pharmaceuticals.