C over a period of 12 hours. The sample temperature was monitored
continuously using a Pt100 sensor. After 4, 8,12, and 24 hours, the samples
were removed from the drying process and the residual volume in the tubes
was determined. The drying process had to be interrupted briefly each time
the samples were removed.
Results of bacteria cultivation
The time required for the cultivation of E. coli HB101 / B. subtilis 168
corresponds to the usual times for 5 ml cultures in
Erlenmeyer flasks (see Figs. 1 and 2). Undelayed growth was possible with
both tube types and bacteria species up to an absorption of 1.8.
Sealed Safe-Lock microcentrifuge tubes (1.5 ml filled with 1ml culture)
were selected as a negative control. The cell concentrations obtained in
these tubes were much lower.
The assumption that evaporation phenomena are independent of the medium
used (LB or water) was confirmed by the results of the growth of E. coli
HB101 (results not shown).
Whereas there was virtually no evaporation with Erlenmeyer flasks that had
been sealed with cellulose stoppers, the membrane-lid tubes displayed negligible
evaporation values (< 7 % in 6 hours; approx. 20 % in 16 hours) (results
During both cultivation processes, no differences in cell morphology were
noted with E. coli HB101 or with B. subtilis 168.
Results of freeze-drying
The speed at which solutions are freezedried in membrane-lid tubes corresponds
to the requirements of standard pro
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