What is the principle of strains preservation? How should I keep it?

Microbial Technology Channel: The basic principle of bacterial preservation is to reduce the metabolic action of microorganisms to a very low limit, so that it is inabernatedFrom the microbial itself, is to select the typical species of good purebred, the best use of their dormant body (such as spores, spores, etc.), such as spores or spores of microorganisms, to produce spores or spores after they are preserved; Most strains are designed to preserve them based on these factors or some of themmicrobes have the characteristics of easy variation, therefore, in the process of preservation, the metabolism of microorganisms must be in the least active or relatively static state, but not to die, in order to make it do not mutate and maintain the ability to live in a certain period of time, so as to achieve the purpose of preservationmoisture is vital to biochemical reactions and all life activities, so it is self-evident that drying, especially deep dryness, plays a primary role in preservationPhosphorus pentoxide, calcium chloride and silicone are good desiccants, of course, a high vacuum can also achieve both the goal of oxygen decommissioning and deep dryingin addition to moisture, low temperature is another important condition in the preservationThe temperature limit for microbial growth is about 30 degrees C, but the temperature limit that can perform enzymatic reactions in aqueous solutions is around -140 degrees CThis may be one of the main reasons why, in watery conditions, it is difficult to preserve microbes even at lower temperatures for longer periods of timeIn cryogenic preservation, cell size is generally more sensitive to low temperature than smaller ones, while cell-less people are more sensitive to cell walls than those with cell wallsThe reason is related to the low temperature that the moisture in the cell forms ice crystals, which causes damage to the cellular structure, especially the cell membraneIf frozen at low temperature (not a general refrigerator), the appropriate use of the method of freezing, can be caused by small ice crystals can reduce the damage to the cellsWhen it is removed from low temperatures and starts to heat up, the ice crystals grow again, so rapid warming can also reduce damage to cellsof course, the most suitable freezing speed and heating rate of different microorganisms are also differentThe medium at freezing also has a significant effect on cell damage or notFor example, about 0.5mol/L glycerin or metformin can penetrate cells and protect cells by reducing strong dehydration; macromolecules such as dextrin, serum albumin, skimmed milk, or polyethylene pyrethroony (PVP) may not penetrate cells, but may prevent cell membrane frostbite by binding to the cell surfaceIn practice, it is found that the effect is more ideal when preserving with a lower temperature, such as liquid nitrogen temperature (-195 degrees C) is better than dry ice temperature (-70 degrees C), -70 degrees C is better than -20 degrees C, and -20 degrees C is better than 4 degrees C