Is there a cheaper alternative to IPTG?

Michael Galperin Galperin at biotek.mcb.uconn.edu
Tue Dec 13 19:57:44 EST 1994


In article <tan-0812941554100001 at smac.ethz.ch> tan at mol.biol.ethz.ch (Song Tan) writes:

>Someone in our lab tried unsuccessfully to use lactose instead of IPTG for
>induction a while ago and decided the problem was pH changes as the
>lactose was hydrolyzed by the cells.  IPTG doesn't suffer from this
>problem because it is nonhydrolyzable, of course.  
>Still, I've love to hear if others have been successful in replacing IPTG
>with lactose.

	I used lactose for a while but didn't compare the level of induction 
achieved with what IPTG might give. Here's my $0.02:
1. IPTG conc. can be decreased from 1 mM to 50-100 uM without substantial
change in induction level
2. Lactose can leak into the cell with Km in millimolar range and needs only 
beta-gal to be converted into the inducer. So it is not necessary that the 
cells metabolise lactose, presence of lacZ (or truncated lacZ plus alpha-
peptide) should do the trick.
3. Lactose can be added shortly (say, 1 hour) before harvesting the cells.
This should alleviate any problems with its metabolism.

Michael Galperin                           <galperin at biotek.mcb.uconn.edu>
Dept. Mol. Cell Biol. U-125                      Phone: 203-486-4330
The University of Connecticut                      Fax: 203-486-4331



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