Synthetic 2,3-butanediol pathway integrated using Tn7-tool and powered via elimination of sporulation and acetate production in acetogen biocatalyst.

Acetogen Clostridium sp. MT1802 originally producing 336-mM acetate from inorganic carbon of CO₂/CO was engineered to eliminate acetate production and sporulation using Cre-lox66/lox71-approach. The recombinant started producing 105-mM formate expressing synthetic formate dehydrogenase integrated in two copies. Formate-producing recombinant was further engineered to express synthetic formate acetyltransferase, acetolactate synthase, acetolactate decarboxylase, and alcohol dehydrogenase integrated in two copies each using Tn7 tool. The resulted recombinant started producing 102-mM 2,3-butanediol (23BD). 23BD production was confirmed in five independent single step fermentation runs 25 days long each in five repeats using syngas blend 60 % CO and 40 % H₂ (v/v) (p <0.005). 23BD production was 78 % if only CO₂/H₂ blend was fed instead of syngas (p <0.005). 23BD from CO₂/H₂ blend might serve as a commercial route to mitigate global warming in proportion to CO₂ fermentation scale worldwide.