[Knockout of the ptsG gene in engineered Escherichia coli for homoethanol fermentation from sugar mixture]

To realize the simultaneous fermentation of xylose and glucose, ptsG (one of the glucose-PTS genes) was deleted from the engineered ethanologenic Escherichia coli SZ470 (deltapflB, deltafrdABCD, deltaackA, deltaldhA), resulting in loss of glucose effect in the mutant SZ470P (deltaptsG). When tested in 5% mixture of glucose (2.5%) and xylose (2.5%), SZ470P simultaneously used glucose (13 g/L) and xylose (20 g/L) whereas the parent strain SZ470 sequentially used glucose (25 g/L) then xylose (5 g/L). Upon completion of the fermentation, both strains achieved similar product yield of 89%. SZ470P produced 15.01 g/L of ethanol, which was 14.32% higher than that produced by SZ470 (12.86 g/L). Deleting ptsG gene enabled the mutant strain SZ470P to simultaneously use both glucose and xylose and achieve better ethanol production.