Syngas biological transformation into hydroxyectoine.

Syngas from the gasification of organic wastes represents a promising feedstock for fostering a sustainable bioeconomy. However, its potential is currently constrained by the low-value products generated. Osmolytes, such as hydroxyectoine, are high-value compounds, however, their biological production as isolated osmolytes is not yet cost-effective. This study utilized shotgun genomics and laboratory validation to find a carboxydotrophic, halotolerant bacterium, Hydrogenibacillus schlegelii, that could produce hydroxyectoine using H2, CO and CO2 as the sole source of energy and carbon. Subsequently, NaCl concentration, temperature and syngas composition were optimized in semi-continuous bioreactors. Optimal conversion of CO into hydroxyectoine occurred at a gas composition of 70 %:10 % CO:H2 (v/v) (44.8 ± 10.1 mghydroxyectoine·gbiomass-1). NaCl concentrations of 5 % significantly enhanced hydroxyectoine content (46.7 ± 9.5 mghydroxyectoine·gbiomass-1), but negatively affected gas consumption. This study opens new perspectives for the valorisation of syngas into hydroxyectoine, and for new cell platforms for pharmaceutical production based on syngas.