Metabolic Engineering of for High-Yield Production of ()-1,3-Butanediol.

1,3-Butanediol (1,3-BDO) is an important C4 platform chemical widely used as a solvent in cosmetics and a key intermediate for the synthesis of fragrances, pheromones, and pharmaceuticals. The development of sustainable bioprocesses to produce enantiopure 1,3-BDO from renewable bioresources by fermentation is a promising alternative to conventional chemical routes and has aroused great interest in recent years. Although two metabolic pathways have been previously established for the biosynthesis of ()-1,3-PDO, the reported titer and yield are too low for cost-competitive production. In this study, we report the combination of different metabolic engineering strategies to improve the production of ()-1,3-BDO by , including (1) screening of key pathway enzymes; (2) increasing NADPH supply by cofactor engineering; (3) optimization of fermentation conditions to divert more flux into 1,3-BDO pathway; (4) reduction of byproducts formation by pathway engineering. With these efforts, the best engineered strain can efficiently produce ()-1,3-BDO with a yield of 0.6 mol/mol glucose, corresponding to 60% of the theoretical yield. Besides, we also showed the feasibility of aerobically producing 1,3-BDO via a new pathway using 3-hydroxybutyrate as an intermediate.