Efficient free fatty acid production from woody biomass hydrolysate using metabolically engineered Escherichia coli

•Engineered E. coli can synthesize fatty acids from glucose and xylose simultaneously.•The yield of free fatty acids based on xylose reached 20.71%.•The yield of free fatty acids based on mixed sugar reached 24.91%.•3.79 g/L FFAs was produced from commercial hydrolysate with high yield (21.42%).

Four engineered Escherichia coli strains, ML103(pXZ18), ML103(pXZ18Z), ML190(pXZ18) and ML190(pXZ18Z), were constructed to investigate free fatty acid production using hydrolysate as carbon source. These strains exhibited efficient fatty acid production when xylose was used as the sole carbon source. For mixed sugars, ML103 based strains utilized glucose and xylose sequentially under the carbon catabolite repression (CCR) regulation, while ML190 based strains, with ptsG mutation, used glucose and xylose simultaneously. The total free fatty acid concentration and yield of the strain ML190(pXZ18Z) based on the mixed sugar reached 3.64 g/L and 24.88%, respectively. Furthermore, when hydrolysate from a commercial plant was used as the carbon source, the strain ML190(pXZ18Z) can produce 3.79 g/L FFAs with a high yield of 21.42%.