Guyparkeria halophila: Novel cell platform for the efficient valorization of carbon dioxide and thiosulfate into ectoine.

Utilizing carbon dioxide (CO) for valuable chemical production is key to a circular economy. Current processes are costly due to limited microorganism use, low-value products, and the need for affordable energy. This study addresses these challenges by using industrial contaminants like thiosulfate (SO) for CO conversion into ectoines. Ectoines, are important ingredients as pharmaceuticals and cosmetics. Here, six microbial genomes were identified as potential candidates to valorize CO and SO into ectoine. After laboratory validation at 3 % NaCl, the fastest-growing strain, Guyparkeria halophila, was optimized at 6 %, 9 %, and 15 % NaCl, showing the highest specific ectoine contents (mg g) at 15 %. Batch bioreactors, combining optimal conditions, achieved maximum specific ectoine contents of 47 %. These results not only constitute the highest ectoine content so far reported by autotrophs and most of heterotrophs, but also the first proof of a novel valorization platform for CO and SO, focused on pharmaceuticals production.