[Immunology] Need Advice on Freeze Drying

Ashton, Robert via immuno%40net.bio.net (by ashton At src.sk.ca)
Mon Nov 27 10:16:02 EST 2006

  Good morning.  I am running an FTS durastop / duradry lyophilizer here
in our fermentation pilot plant for the Saskatchewan Research Council up
here in Canada.  We are working on a live E coli vaccine, so the
material to be freeze-dried is a TFF concentrated microbial culture
diluted 1:1 with a Dextrin/Sucrose FD medium.  The amounts to be
lyophilized are 5 mls in 20ml vials.  Problem is , we are running the
vials in a tray which is sealed inside a large paper autoclave bag to
maintain sterility during the lyophilisation.  

  I can only seem to get two trays (bagged) to within 4 or 5 % of the
target moisture content.  The vials seem nice and dry, uniform in color
as well, but the cakes inside the vials do tend to have a bit of a hill
in the middle of the cake on the top surface and the moisture readings
as performed in a vac oven are coming out at 10% instead of the required

  My programmed cycle is -30 for 60 min / atmos.  Then -20 for 60 min /
2000mtorr.  Then -10 for 120 min / 880 mtorr.  Then 0C for 120min /
0mtorr.  The secondary cycle kicks in to warm the vials to a 20C
endpoint at 0-10 mtorr.  The entire cycle takes about 18 hours.  The
problem is, I can not seem to get the moisture down the last required
5-6%.  I have been playing with the cycles but everything I adjust seems
to make things worse not better.  I am afraid I will run out of material
to test with before I get the cycle worked out.  If you have any
suggestions they would be much appreciated.

  Have a great day. 

Robert D Ashton 
Ag-Biotech, Fermentation 
Saskatchewan Research Council 
125, 15 Innovation BLVD 
Saskatoon, Sk., Canada 
S7N 2X8 
ashton At src.sk.ca 
(306) 933-5103 
(cell) 222-8493 

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