Increased Flux of Lipid Metabolism Enhances Bioethanol Fermentability and Inhibitor Tolerance of Xylose-Utilizing Zymomonas mobilis

Abstract

The microbial production of fuel ethanol is an attractive and sustainable biotechnological approach. This study presents a metabolic engineering strategy of Zymomonas mobilis aimed at coproducing bioethanol and fatty acids. The increased flux of fatty acids stabilizes the cell membrane and thus counteracts the progressively higher ethanol toxicity. In a glucose medium, the highest ethanol titer achieved was 146.7 g/kg of broth, surpassing the wild-type Z. mobilis CP4 and angel yeast by 30% and 45%, respectively. The recombinant strain exhibited a total fatty acid titer of 0.4 g/L from 230 g/L total sugar solution (5 L bioreactor), representing a 12-fold increase compared to the wild-type Z. mobilis CP4. Furthermore, when using a 4:2:1 mixture of glucose: xylose: mannose (w/v), an ethanol concentration of 142.8 g/kg of broth was attained, only 2.66% lower than that of the glucose-only medium. These findings highlight the enormous potential of this genetically engineered strain for the sustainable production of ethanol and fatty acids from lignocellulosic renewable carbon sources.