Heterotrophic and autotrophic production of L-isoleucine and L-valine by engineered Cupriavidus necator H16.

Advancement in commodity chemical production from carbon dioxide (CO) offers a promising path towards sustainable development goal. Cupriavidus necator is an ideal host to convert CO into high-value chemicals, thereby achieving this target. Here, C. necator was engineered for heterotrophic and autotrophic production of L-isoleucine and L-valine. Citramalate synthase was introduced to simplify isoleucine synthesis pathway. Blocking poly-hydroxybutyrate biosynthesis resulted in significant accumulation of isoleucine and valine. Besides, strategies like key enzymes screening and overexpressing, reducing power balancing and feedback inhibition removing were applied in strain modification. Finally, the maximum isoleucine and valine titers of the best isoleucine-producing and valine-producing strains reached 857 and 972 mg/L, respectively, in fed-batch fermentation using glucose as substrate, and 105 and 319 mg/L, respectively, in autotrophic fermentation using CO as substrate. This study provides a feasible solution for developing C. necator as a microbial factory to produce amino acids from CO.