Freeze-drying preservation
The preservation method is to sublimate the bacterial liquid in a frozen state.
Finally, a dried sample of the cells was obtained. It also has dry, low temperature and anoxic strain preservation conditions. Therefore, the microbial strain can be preserved for a long period of time, and the freeze-dried strain is sealed in a small ampoule, thereby avoiding contamination during storage. It is also convenient for large-scale preservation. It is currently widely recognized as a method of preservation of strains. However, the operation of the method is relatively cumbersome and technically demanding.
According to the literature, except for filamentous fungi that produce spores without mycoplasma, it is not suitable for this method. Most other microorganisms, such as viruses, bacteria, actinomycetes, yeasts, filamentous fungi, etc., can be lyophilized and preserved. Many strains can be preserved for more than 10 years using this method.
The vacuum freeze-drying device has various forms, and the vacuum dryer with a single tube type, a manifold type, a bell type, a centrifugal type, a cabin type, and the like can be selected for the work required for the report. The more the type of the arrangement, the larger the amount of processing and the more complex the device.
The survival rate of lyophilized strains is affected by many aspects, and different organisms are not able to withstand the process of freezing. Therefore, some strains are not suitable for preservation by lyophilization. The culture conditions and bacterial age before lyophilization are also influencing factors. Cells cultured to stable phase under suitable conditions and mature spores have strong tolerance to lyophilization. Promote the use of more concentrated bacterial suspension. Although its survival rate is low, the absolute amount is relatively high. Protective squeezing has a great impact on survival, and the protective effect is closely related to the chemical structure of the protective agent. Effective protection Liu has a strong affinity for fine saturated water. Skim milk as a protective agent has satisfactory results for a variety of microorganisms. Slow freezing will damage cells, and freezing speed is too fast (freezing in a few seconds) It will form ice crystals in the cells, damage the cell membrane and affect survival. Freeze-dried tubes should be protected from light, especially to avoid direct light. Proper recovery of culture conditions can increase survival.
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