Super Optimal Broth


Super Optimal Broth is a nutrient-rich bacterial growth medium used for microbiological culture, generally of Escherichia coli. It was developed by Douglas Hanahan in 1983 and is an adjusted version of the commonly used LB medium. Growth of E. coli in SOB or SOC medium results in higher transformation efficiencies of plasmids.
Super Optimal broth with Catabolite repression is SOB with added glucose.

Composition

SOB

In addition to the SOB contents, SOC also contains 20mM glucose
Alternatively, SOB and SOC can be made by adding small amounts of concentrated magnesium chloride and glucose solutions to pre-prepared SOB.

pH adjustment

For maximum effectiveness, SOB/SOC media should have its pH adjusted to 7.0 by adding concentrated sodium hydroxide. The original literature states that the pH of the final medium should be between 6.8 and 7.0.

Sterilization

Finally, the SOB medium should be autoclaved at 121 °C to ensure sterility. The components of SOC medium should not be autoclaved together because the high temperature can cause the glucose to react with tryptic peptides, compromising the quality. SOB and magnesium and glucose additive solutions can be autoclaved separately and mixed afterwards to final concentrations. Complete SOC can be filter sterilized through a 0.22 μm filter.