During my previous position at a contract facility, we used a 700 Watt
microwave at a setting of 50% for 5 minutes.  Then at 5 minute intervals we
would use a sterile pipette to slice up any large chunks of media and
re-heat.  Because we purchased all of our media in 500mL bottles from Remel
($$$), we tried not to waste any unused agar.  To determine if we could
re-microwave the media without any effect on growth promotion, we embarked on
a study using quanti-cult organisms (10-100cfu).  We did this for each USP
organism for up to three microwave liquefying cycles, but only for SDA and
TSA.  I left the company before the entire study was complete, but
preliminary data looked very promising for up to three re-heats.  I think the
key was to find the lowest setting for liquefying in a reasonable amount of
time, say 15 minutes.

Nancy A. Fulginiti MT(ASCP)


------------------
The PMFList (http://microbiol.org/PMFList_info.htm) is operated from
The Microbiology Network (http://microbiol.org) and supported by
our sponsors (http://microbiol.org/sponsor.htm) as a service to
the scientific community.