How To Freeze Dry a Bacterial Culture

Grow an overnight culture, or lawn, of the microorganism on LB or other appropriate nutrient agar plate.

Prepare sterile crimp-cap vials by autoclaving ahead of time, with the caps (rubber stopper) placed loosely on top. Place paper labels printed with the culture identification inside the tubes prior to autoclaving. Alternatively, use tubes with caps designed for sterility.

Add 4 mL lyophilization buffer to the plate. If necessary, the cells can be suspended using a sterile glass rod.

Quickly transfer the culture suspension to the sterilized vials. Add approximately 1.5 mL per vial. Seal with the rubber cap.

Freeze the culture suspension inside the vials by placing the vials in a -20 degrees Celcius freezer.

Once the cultures are frozen, prepare the freeze drier by turning it on and allowing time for the appropriate temperature and vaccum conditions to stabilize. Of course, this is done according the manufacturer's instructions for the particular brand of freeze drier you are using.

Carefully and asceptically place the vial caps loosely on top of the vials, so moisture can escape during the freeze drying process, and place the vials into a freeze drier chamber. Apply the vaccum to the chamber according to the manufacturer's instructions.

Allow the culture time to completely lyophilize (dry out). This may take anywhere from a couple hours to overnight, depending on the volume of each sample and how many samples you have.

Remove the samples from the freeze drier chamber according to the manufacturer's instructions, and immediately seal the vials with the rubber caps, then the crimp tops.

Store the lyophilized culture collection at room temperature.