Conversion efficiency of bioethanol from levoglucosan was improved by the newly engineered Escherichia coli

Bioethanol produced from waste lignocellulosic biomass is a promising renewable fuel in environmental and sustainable views. The thermochemical process that can readily decompose lignocellulosic biomass to carbohydrate-rich bio-oil is more appealing compared to biochemical process due to its low costs and less time. However, levoglucosan, the dominant carbohydrate present in the bio-oil, is problematic to be efficiently converted to bioethanol by native and recombinant microorganisms. Here, a synthetic metabolic pathway based on the heterologous genes encoding levoglucosan kinase, pyruvate decarboxylase, and alcohol dehydrogenase, was constructed and introduced into Escherichia coli to generate new platforms for ethanol production from levoglucosan. The engineered E. coli strains overexpressing levoglucosan kinase could, for the first time, completely consume 1-2% (wt/vol) levoglucosan present in the minimal media to produce ethanol with relatively high yield; while E. coli LGE2 exhibited the maximal ethanol yield of 0.43 g/g levoglucosan, rising by similar to 23% compared to the only existing recombinant strain E. coli KO11 + lgk. Although levoglucosan utilization was inferior to the utilization of other substrates like fructose and complex media, our results suggest that desired high-yield bioethanol production from levoglucosan-based minimal media could be efficiently achieved by the newly engineered strains, which could provide a solution for complete bioethanol fermentation from the thermochemically decomposed biomass feedstock.