Super Optimal broth (SOB) is a nutrient-rich microbiological media used for bacterial growth, typically with recombinant E. coli. Compared to lysogeny broth (LB) media, SOB media results in higher plasmid transformation efficiencies. SOB media has more peptone compared to LB media and includes magnesium sulfate and potassium chloride. SOB media differs from SOC (SOB media with catabolite repression) media due to its lack of glucose. Like other undefined media prepared from mixtures of digested proteins and yeast extracts, there can be variability in formulations due to processing changes and raw material sources. Therefore, cultures’ growth rates and productivities may differ when different vendor’s media are used in otherwise identical experiments.
The extremely high variability in the individual media components’ concentrations suggests little similarity across different commercial sources of SOB media. Teams should test media before use, and especially when switching suppliers, to maintain uniformity across experiments.