Metabolic engineering has been very successful in addressing pathway optimization for localized branches, but multigenic or poorly understood traits have remained a challenge. To overcome these limitations, we have successfully delivered a method that introduces global transcriptomic changes, thereby generating enhanced diversity at the phenotypic level. This method contrasts with others for its easy implementation and for the tractability and transferability of the genetic modifications. Furthermore, the global nature of the generated diversity imparts significant versatility to the resulting libraries. We have extended the technique to include other global regulators and other species with promising results. We have applied it to Lactobacillus plantarum for overcoming its poor resistance to high lactic acid conditions, especially at low pH. With a single round of mutagenesis, the best strain increased its growth rate in high lactic acid by 2.6-fold, and the L-lactate production at low pH by 90%. Other strains with different improvements have resulted from screening the libraries in other conditions. As such, this system has great potential for becoming a routine tool in metabolic engineering.