A miniaturized method for freeze-drying of microorganisms in glass capillary tubes

Abstract

A successful method for freeze-drying of various sensitive bacteria and yeasts in glass capillary tubes for long-term preservation is described. The dried microbiological cells proved viable and stable after reactivation. In the case of capillaries which were not sealed under vacuum, poor viabilities were demonstrated after storage at relatively higher temperatures (above 4°C). However, only a slight drop in viability occurred during 6–12 months of storage at −80°C, whereas during storage at −30°C the viability drops were relatively higher. The capillaries sealed under vacuum proved better for storage at relatively higher temperatures as compared to the unsealed capillaries. For recovery, a single sealed capillary was removed without disturbing the parallel samples. The method is first of its kind which describes optimal freeze-drying on miniaturized scale. For long-term storage the pre-dried sensitive microorganisms in glass capillary tubes are ideal for cryopreservation or dry-freezing involving no controlled freezing and thawing. The dried cells in glass capillary tubes can be stored for long-terms at relatively low cost due to less storage space required and it is economical with respect to the transport costs. No immediate reactivation is required before mailing. For the automatic inoculation of fermentors surface sterilized capillary tubes can be crushed mechanically in the growth medium.