GREAT AT SMALL THINGS

Freeze-drying service for long-term storage of bacterial cultures

For biological resource centers (BRCs) maintaining and providing prokaryotes, freeze-drying or lyophilization is generally preferred over cryopreservation as long-term preservation method. A properly freeze-dried bacterial strain can be stored for 30 years and even beyond that without any high cooling expenses during storage or transport. Moreover, freeze-dried bacterial cells can immediately be used after rehydration without any wash steps, in contrary to cryopreservation.

During the freeze-drying process, bacterial cells are first suspended in a lyoprotective solution, followed by a freezing step at -50°C for 3h. By lowering the pressure and adding heat, sublimation starts: ice is converted into water vapor and removed from the bacterial solution. This primary drying phase is performed at -25°C, in order to avoid any melting. Once all ice is removed, a secondary drying is performed at 20°C to remove the remaining unfrozen water. The final residual moisture content of the dried bacterial solution is 1.6% (w/w). To retain an oxygen and moisture free environment, the recipient with dried bacterial cultures is closed under vacuum.

BCCM/LMG offers freeze-drying as a service for third parties, either using BCCM/LMG strains or strains delivered by the customer. The freeze-drying service can be performed in 2 formats: glass ampules or glass vials, each with multiple filling volumes (see table below):

 

 

Ampule

Vial

 

 

   

Filling volumes

100µl

200µl

20 ml

2ml

1ml

200µl

Max. storage time at 4°C     

30 years

2 years

 

Ampules are closed by heat-sealing under vacuum. For revival of the culture, the ampule is broken and liquid medium can be added (see  video: https://www.youtube.com/watch?v=Kc5Q5GNjVYI).

Vials are stoppered under vacuum with a butyl septum and sealed with an aluminum crimp cap. For revival of the culture, you can either pierce the septum with a needle (remove a small part of the crimp cap first) and inject the rehydration solution, or you can remove the septum cap from the vial (remove the full crimp cap first) and add the rehydration solution with a pipette.

 

For prices and other volumes, please contact us at bccm.lmg@UGent.be

Reference:

Peiren J, Buyse J, De Vos P, Lang E, Clermont D, Hamon S, Begaud E, Bizet C, Pascual J, Ruvira MA, Macian MC, Arahal DR (2015) Improving survival and storage stability of bacteria recalcitrant to freeze-drying: a coordinated study by European culture collections. Appl Microbiol Biotechnol 99(8):3559-71 doi:10.1007/s00253-015-6476-6