2.4. Growth, preservation, storage and recovery
The ability of each media to support sufficient growth for
preservation and storage was determined. Bacteria, yeast cells and fungal spores were grown on TSA as well as each
vegetable-based agar media and grown under appropriate
conditions. A concentrated cell suspension was made in the
corresponding growth medium and mixed 1:1 with a 12% (w/v)
stock solution of glycine-betaine cryoprotectant (Cleland et al.,
2004). The cell suspensions were dispensed into serum vials
and subjected to batch lyophilization. Randomly selected vials
from each lyophilized batch were placed at 37 °C for 4 days to
simulate long-term storage at 4 °C for 5 years (Sakane and
Kuroshima, 1997). The viable load (CFU/mL) for pre- and postlyophilization
vials and vials held in accelerated storage
conditions was determined by suspending the lyophilized pellet
in phosphate buffered saline (PBS). The cell suspension was
diluted with a series of ten-fold dilutions using PBS and appropriate
dilutions were plated onto animal-based TSA. Following
an incubation period optimal for each isolate, colony
density wasmanually counted on plates and the reported numbers
represent the average viable counts for at least three serum
vials.