[Objective] To explore different preservation methods of recombinant E.coli and find out the optimal conditions for preservation. [Method] The recombinant E.coli DH5α transformed pcDNA3 were respectively preserved at 4 ℃ and -70 ℃, and the activity was determined after different time. [Result] The number of living E.coli with high dilutions preserved at 4 ℃ was gradually increased within the first 7 d, peaked on Day 7, and then gradually decreased. The number of living E.coli, which were preserved in 8% glycerol at -70 ℃ when OD600 at 0.8, were significantly higher than that of other groups after different preservation time. [Conclusion] The optimal storage time was 7 d for recombinant E.coli at 4 ℃. For preservation at -70 ℃, the bacteria should be in logarithmic growth phase and preserved in 8% glycerol.
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