LB Broth, Auto-Induction Medium

LB Broth (Auto-Induction Medium) is a dehydrated powder for the preparation of LB Broth without trace elements, supplemented with glucose and alpha lactose for the auto induction of protein expression under the control of IPTG-inducible promoters in E. coli. The Auto-Induction Medium (AIM) provides an efficient means of protein expression that requires far less attention by the user than conventional IPTG induction.

Heterologous protein expression is often carried out in bacterial systems in which the expression is under the control of an IPTG-inducible promoter, such as the Lac promoter. Cells are grown until a desired density is reached and then protein expression is induced by the user adding IPTG to the medium. With the Auto-Induction Medium, it is no longer necessary to monitor cell density and to add IPTG at the proper stage, as the medium contains an optimized ratio of glucose and alpha lactose as carbon sources.

Glucose, serving as a repressor of the Lac operon, prevents uptake of alpha lactose (hence and IPTG) and is metabolized preferentially during growth, promoting high cell density. Once glucose is depleted, lactose enters the cell where it is converted by ßgalactosidase into allolactose. Allolactose in turn serves as the inducer of the IPTG-inducible promoter, resulting in protein expression. This system offers unmatched convenience and simplifies manual or automatic induction and analysis of multiple clones compared to conventional IPTG induction.

Formulation (g/l)

• Tryptone: 10.00
• Yeast Extract: 5.00
• MgSO₄: 0.15
• (NH₄)₂SO₄: 3.30
• KH₂PO₄: 6.80
• Na₂HPO₄: 7.10
• Glucose: 0.50
• Alpha Lactose: 2.00
• Final pH (25°C): 7.0 ± 0.2