Omics-based metabolic engineering of Zymomonas mobilis for production of 2,3 butanediol from lignocellulosic biomass sugars

Zymomonas mobilis is an ethanologen well-known for both its high specific glucose uptake rate and rapid catabolism and is engineered to metabolize the major biomass sugars, including glucose and the C5 sugars, xylose and arabinose. We seek to take the advantage of the organism’s metabolic capabilities and are working to redirect the carbon flow to produce other desirable chemicals, such as 2,3 butanediol (BDO).  2,3 Butanediol is not only a bulk chemical building block, but also can be converted to butenes by deoxydehydration which can then be oligomerized in high yields to produce gasoline, diesel, and jet fuels. In this work, genomic and pathway analyses have been carried out to identify heterologous genes for BDO pathway engineering in Z. mobilis. Our result demonstrated that Z. mobilis can produce 2,3 butanediol from glucose and xylose; as well as mixed C6/C5 sugar streams derived from the Deacetylation and Mechanic Refining (DMR) pretreatment and enzymatic hydrolysis deconstruction process. In addition, we have improved the BDO titer through our initial pathway gene optimization efforts. Further optimization including pathway gene and promoter selection, carbon redirection, fermentation condition evaluation, and RNA-Seq based transcriptomics is underway to further understand the bottleneck for BDO production and achieve higher BDO titers. Challenges and potential solutions will also be discussed.