Is there a cheaper alternative to IPTG?

[PANIAGUA SOLIS JORGE FERNANDO]

Hello bio.net.ers:
 I am trying to induce moderate quantities (about 5 liter cultures) of an 
E. coli strain with a plasmid containing a gene controled by the lac 
promotor. I dont want to finish our next year supply of IPTG and I would 
like to ask if anyone knows about a cheaper alternative of lac induction. 
The E. coli starin is DH5 alpha. Thanks very much from a warm Mexican 
graduate student.   Manuel Carrera, jpaniagf at condor.dgsca.unam.mx