Influence of heterologous 2,3-butanediol pathway engineering and oxygen level on host metabolism of Zymomonas mobilis

2,3 butanediol (2,3-BDO) is a bulk chemical building block, and can be upgraded in high yields to gasoline, diesel, and jet fuel. Production of 2,3-BDO from lignocellulosic biomass can be an efficient route to meet the need of biological upgrading of sugars to advanced hydrocarbons. In this study, we take the advantage of high specific glucose uptake rate and rapid catabolism of the well-known model ethanologenic bacterium Z. mobilis to redirect the carbon flow to produce 2,3-BDO. Bioinformatics analysis was carried out to identify potential homologous genes existing in Z. mobilis and to pinpoint bottlenecks for high 2,3-BDO production using public and “in-house” systems biology datasets. Different combinations of 2,3-BDO biosynthesis metabolic pathways using genes from different bacterial species have been constructed and introduced into Z. mobilis. Our result demonstrated that carbon flux can be deviated from ethanol production into 2,3-BDO biosynthesis, and all three heterologous 2,3-BDO biosynthesis pathway genes are essential to efficiently redirect pyruvate from ethanol production for high 2,3-BDO production in Z. mobilis. The down-selection of current best gene combination helps Z. mobilis reach the 2,3-BDO production of more than 10 g/L from glucose and xylose as well as mixed C6/C5 sugar streams derived from the Deacetylation and Mechanic Refining (DMR) process. This study also reveals the impact of heterologous pathway engineering and oxygen level on host metabolism, and provides guidance for future metabolic engineering efforts to continue boost 2,3-BDO titer, which also could be served as a paradigm for future metabolic engineering practice.