In E. coli, the obvious and successful strategy to increase ethanol production has been the expression of the ethanologenic pathway from Z. mobilis, with the genes encoding PDC and ADH II organized in a single plasmid, the PET operon [73, 76], the latter integrated in the chromosome [134]. Subsequent selection of mutants with high ADH activity and disrupted fumarate reductase (for succinate produc­tion) originated KO11 strain that produces ethanol at a yield of 95% [135]. However, this strain is unable to grow in ethanol concentrations of 3.5% [199]. Evolutionary genetic engineering strategies were then, applied during a 3-month period, by alternating selection for ethanol tolerance in liquid media and selection for increased ethanol production in solid medium [199]. The resulting strain, LY01, was able to grow in ethanol concentrations of 5%. Coincidentally, this strain became more resistant to aldehydes (including HMF and furfural), organic acids, and alcohol compounds i. e. found in hemicelluloses hydrolysates [201-203]. However, LY01 strain performed poorly in mineral medium compared to rich medium [199]. To avoid dependence on nutritional supplementation, a new strain was produced from SZ110 [200], while the parental strain KO11 was engineered for lactate production in mineral medium [211].