Request for Clarification Lactose/skimmed milk Use in Protocol instead of IPTG?

03 December 2024 1 3K Report

Escherichia coli BL21 (DE3) bacteria were induced using 1 mM IPTG or 1.0% (w/v) skimmed milk. However, I found it a bit unclear how lactose IS USED

Michael J. Benedik

Milk contains lactose so that is inducing the lac operon. But induction by lactose should only work in a strain that is also expressing LacZ which converts lactose to allolactose, the actual inducer of the operon. BL21 is in fact LacZ+ so this should work. However IPTG is really cheap these days and I'm not sure why someone would use milk as an inducer since you don't really know how the concentration of lactose in the milk.

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